Amy M. Kerkvliet, MD

To the Editor:

Many types of neoplasms can show aberrant immunoreactivity or unexpected expression of markers.¹ Malignant melanoma is a tumor that can show not only aberrant immunohistochemical staining patterns but also notable histologic diversity,^1,2 which often makes the diagnosis of melanoma challenging and ultimately can lead to diagnostic uncertainty.²

The incidence of malignant melanoma continues to grow.³ Maintaining a high degree of suspicion for this disease, recognizing its heterogeneity and divergent differentiation, and knowing potential aberrant immunohistochemical staining patterns are imperative for accurate diagnosis.

A 36-year-old man presented to a primary care physician with right-sided chest pain, upper and lower back aches, bilateral hip pain, neck pain, headache, night sweats, chills, and nausea. After infectious causes were ruled out, he was placed on a steroid taper without improvement. He presented to the emergency department a few days later with muscle spasms and was found to also have diffuse abdominal tenderness and guarding. The patient’s medical history was noncontributory; he was a lifelong nonsmoker. Laboratory studies revealed elevated levels of alanine aminotransferase and C-reactive protein. Computed tomography of the chest and abdomen revealed innumerable liver and lung lesions that were suspicious for metastatic malignancy. A liver biopsy revealed nests and sheets of metastatic tumor with pleomorphic nuclei, inconspicuous nucleoli, and areas of intranuclear clearing (Figures 1 and 2). Immunohistochemical staining was performed to further characterize the tumor. Neoplastic cells were positive for MART-1 (also known as Melan-A and melanoma-associated antigen recognized by T cells)(Figure 3), SOX10, S-100, HMB-45, and vimentin. Nonspecific staining with CD56 (Figure 4), a neuroendocrine marker, also was noted; however, the neoplasm was negative for synaptophysin, another neuroendocrine marker. Other markers for which staining was negative included pan-keratin, CD138 (syndecan-1), desmin, placental alkaline phosphatase (PLAP), inhibin, OCT-4, cytokeratin 7, and cytokeratin 20. This staining pattern was compatible with metastatic melanoma with aberrant CD56 expression.

BRAF V600E immunohistochemical staining also was performed and showed strong and diffuse positivity within neoplastic cells. A subsequent positron emission tomography scan revealed widespread metastatic disease involving the lungs, liver, spleen, and bones. The patient did not have a history of an excised skin lesion; no primary cutaneous or mucosal lesions were identified.

The patient was started on targeted therapy with trametinib, a mitogen-activated extracellular signal-related kinase kinase (MEK) inhibitor, and dabrafenib, a BRAF inhibitor. The disease continued to progress; he developed extensive leptomeningeal metastatic disease for which palliative radiation therapy was administered. The patient died 4 months after the initial diagnosis.

More than 90% of melanoma cases are of cutaneous origin; however, 4% to 8% of cases present as a metastatic lesion in the absence of an identified primary lesion,⁴ similar to our patient. The diagnosis of melanoma often is challenging; the tumor can show notable histologic diversity and has the potential to express aberrant immunophenotypes.^1,2 The histologic diversity of melanoma includes a variety of architectural patterns (eg, nests, trabeculae, fascicular, pseudoglandular, pseudopapillary, or pseudorosette patterns), cytomorphologic features, and stromal changes. Cytomorphologic features of melanoma can be large pleomorphic cells; small cells; spindle cells; clear cells; signet-ring cells; and rhabdoid, plasmacytoid, and balloon cells.⁵

Melanoma can mimic carcinoma, sarcoma, lymphoma, benign stromal tumors, plasmacytoma, and germ-cell tumors.⁵ Nuclei can binucleated, multinucleated, or lobated and may contain inclusions or grooves. Stroma may become myxoid or desmoplastic in appearance or rarely show granulomatous inflammation or osteoclastic giant cells.⁵ These variations render the diagnosis of melanoma challenging and ultimately can lead to diagnostic uncertainty.

Melanomas typically express MART-1, HMB-45, S-100, tyrosinase, NK1C3, vimentin, and neuron-specific enolase. However, melanoma is among the many neoplasms that sometimes exhibit aberrant immunoreactivity and differentiation toward nonmelanocytic elements.⁶ The most commonly expressed immunophenotypic aberration is cytokeratin, especially the low-molecular-weight keratin marker CAM5.2.⁵ CAM5.2 positivity also is seen more often in metastatic melanoma. Melanomas rarely express other intermediate filaments, including desmin, neurofilament protein, and glial fibrillary acidic protein; expression of smooth-muscle actin is rare.⁵

Only a few cases of melanoma showing expression of neuroendocrine markers have been reported. However, one study reported synaptophysin positivity in 29% (10/34) of cases of primary and metastatic melanoma, making the stain a relatively common finding.¹

In contrast, expression of CD56 (also known as neural-cell adhesion molecule 1) in melanoma has been reported only rarely. CD56 is a nonspecific neuroendocrine marker that normally is expressed on neurons, glial tissue, skeletal muscle, and natural killer cells. Riddle and Bui⁷ reported a case of metastatic malignant melanoma with focal CD56 positivity and no expression of other neuroendocrine markers, similar to our patient. Suzuki and colleagues⁴ also reported a case of melanoma metastatic to bone marrow that showed CD56 expression in true nonhematologic tumor cells and negative immunoreactivity with synaptophysin and chromogranin A.

It is important to document cases of melanoma that express neuroendocrine markers to prevent an incorrect diagnosis of a neuroendocrine tumor.¹ In some cases, distinguishing amelanotic melanoma from poorly differentiated squamous cell carcinoma, neuroendocrine tumor, and lymphoma can be difficult.⁵

The term neuroendocrine differentiation is reserved for cases of melanoma that show areas of ultrastructural change consistent with a neuroendocrine tumor.² Neuroendocrine differentiation in melanoma is not common; its prognostic significance is unknown.⁸ We do not consider our case to be true neuroendocrine differentiation, as the tumor lacked the morphologic changes of a neuroendocrine tumor. Furthermore, CD56 is a nonspecific neuroendocrine marker, and the tumor was negative for synaptophysin.

Melanoma has the potential to show notable histologic diversity as well as aberrant immunohistochemical staining patterns.^1,2 Our patient had metastatic melanoma with aberrant neuroendocrine expression of CD56, which could have been a potential diagnostic pitfall. Because expression of CD56 in melanoma is rare, it is imperative to recognize this potential aberrant staining pattern to ensure the accurate diagnosis of melanoma and appropriate provision of care.

To the Editor:

Many types of neoplasms can show aberrant immunoreactivity or unexpected expression of markers.¹ Malignant melanoma is a tumor that can show not only aberrant immunohistochemical staining patterns but also notable histologic diversity,^1,2 which often makes the diagnosis of melanoma challenging and ultimately can lead to diagnostic uncertainty.²

The incidence of malignant melanoma continues to grow.³ Maintaining a high degree of suspicion for this disease, recognizing its heterogeneity and divergent differentiation, and knowing potential aberrant immunohistochemical staining patterns are imperative for accurate diagnosis.

A 36-year-old man presented to a primary care physician with right-sided chest pain, upper and lower back aches, bilateral hip pain, neck pain, headache, night sweats, chills, and nausea. After infectious causes were ruled out, he was placed on a steroid taper without improvement. He presented to the emergency department a few days later with muscle spasms and was found to also have diffuse abdominal tenderness and guarding. The patient’s medical history was noncontributory; he was a lifelong nonsmoker. Laboratory studies revealed elevated levels of alanine aminotransferase and C-reactive protein. Computed tomography of the chest and abdomen revealed innumerable liver and lung lesions that were suspicious for metastatic malignancy. A liver biopsy revealed nests and sheets of metastatic tumor with pleomorphic nuclei, inconspicuous nucleoli, and areas of intranuclear clearing (Figures 1 and 2). Immunohistochemical staining was performed to further characterize the tumor. Neoplastic cells were positive for MART-1 (also known as Melan-A and melanoma-associated antigen recognized by T cells)(Figure 3), SOX10, S-100, HMB-45, and vimentin. Nonspecific staining with CD56 (Figure 4), a neuroendocrine marker, also was noted; however, the neoplasm was negative for synaptophysin, another neuroendocrine marker. Other markers for which staining was negative included pan-keratin, CD138 (syndecan-1), desmin, placental alkaline phosphatase (PLAP), inhibin, OCT-4, cytokeratin 7, and cytokeratin 20. This staining pattern was compatible with metastatic melanoma with aberrant CD56 expression.

BRAF V600E immunohistochemical staining also was performed and showed strong and diffuse positivity within neoplastic cells. A subsequent positron emission tomography scan revealed widespread metastatic disease involving the lungs, liver, spleen, and bones. The patient did not have a history of an excised skin lesion; no primary cutaneous or mucosal lesions were identified.

The patient was started on targeted therapy with trametinib, a mitogen-activated extracellular signal-related kinase kinase (MEK) inhibitor, and dabrafenib, a BRAF inhibitor. The disease continued to progress; he developed extensive leptomeningeal metastatic disease for which palliative radiation therapy was administered. The patient died 4 months after the initial diagnosis.

More than 90% of melanoma cases are of cutaneous origin; however, 4% to 8% of cases present as a metastatic lesion in the absence of an identified primary lesion,⁴ similar to our patient. The diagnosis of melanoma often is challenging; the tumor can show notable histologic diversity and has the potential to express aberrant immunophenotypes.^1,2 The histologic diversity of melanoma includes a variety of architectural patterns (eg, nests, trabeculae, fascicular, pseudoglandular, pseudopapillary, or pseudorosette patterns), cytomorphologic features, and stromal changes. Cytomorphologic features of melanoma can be large pleomorphic cells; small cells; spindle cells; clear cells; signet-ring cells; and rhabdoid, plasmacytoid, and balloon cells.⁵

Melanoma can mimic carcinoma, sarcoma, lymphoma, benign stromal tumors, plasmacytoma, and germ-cell tumors.⁵ Nuclei can binucleated, multinucleated, or lobated and may contain inclusions or grooves. Stroma may become myxoid or desmoplastic in appearance or rarely show granulomatous inflammation or osteoclastic giant cells.⁵ These variations render the diagnosis of melanoma challenging and ultimately can lead to diagnostic uncertainty.

Melanomas typically express MART-1, HMB-45, S-100, tyrosinase, NK1C3, vimentin, and neuron-specific enolase. However, melanoma is among the many neoplasms that sometimes exhibit aberrant immunoreactivity and differentiation toward nonmelanocytic elements.⁶ The most commonly expressed immunophenotypic aberration is cytokeratin, especially the low-molecular-weight keratin marker CAM5.2.⁵ CAM5.2 positivity also is seen more often in metastatic melanoma. Melanomas rarely express other intermediate filaments, including desmin, neurofilament protein, and glial fibrillary acidic protein; expression of smooth-muscle actin is rare.⁵

Only a few cases of melanoma showing expression of neuroendocrine markers have been reported. However, one study reported synaptophysin positivity in 29% (10/34) of cases of primary and metastatic melanoma, making the stain a relatively common finding.¹

In contrast, expression of CD56 (also known as neural-cell adhesion molecule 1) in melanoma has been reported only rarely. CD56 is a nonspecific neuroendocrine marker that normally is expressed on neurons, glial tissue, skeletal muscle, and natural killer cells. Riddle and Bui⁷ reported a case of metastatic malignant melanoma with focal CD56 positivity and no expression of other neuroendocrine markers, similar to our patient. Suzuki and colleagues⁴ also reported a case of melanoma metastatic to bone marrow that showed CD56 expression in true nonhematologic tumor cells and negative immunoreactivity with synaptophysin and chromogranin A.

It is important to document cases of melanoma that express neuroendocrine markers to prevent an incorrect diagnosis of a neuroendocrine tumor.¹ In some cases, distinguishing amelanotic melanoma from poorly differentiated squamous cell carcinoma, neuroendocrine tumor, and lymphoma can be difficult.⁵

The term neuroendocrine differentiation is reserved for cases of melanoma that show areas of ultrastructural change consistent with a neuroendocrine tumor.² Neuroendocrine differentiation in melanoma is not common; its prognostic significance is unknown.⁸ We do not consider our case to be true neuroendocrine differentiation, as the tumor lacked the morphologic changes of a neuroendocrine tumor. Furthermore, CD56 is a nonspecific neuroendocrine marker, and the tumor was negative for synaptophysin.

Melanoma has the potential to show notable histologic diversity as well as aberrant immunohistochemical staining patterns.^1,2 Our patient had metastatic melanoma with aberrant neuroendocrine expression of CD56, which could have been a potential diagnostic pitfall. Because expression of CD56 in melanoma is rare, it is imperative to recognize this potential aberrant staining pattern to ensure the accurate diagnosis of melanoma and appropriate provision of care.

To the Editor:

Many types of neoplasms can show aberrant immunoreactivity or unexpected expression of markers.¹ Malignant melanoma is a tumor that can show not only aberrant immunohistochemical staining patterns but also notable histologic diversity,^1,2 which often makes the diagnosis of melanoma challenging and ultimately can lead to diagnostic uncertainty.²

The incidence of malignant melanoma continues to grow.³ Maintaining a high degree of suspicion for this disease, recognizing its heterogeneity and divergent differentiation, and knowing potential aberrant immunohistochemical staining patterns are imperative for accurate diagnosis.

A 36-year-old man presented to a primary care physician with right-sided chest pain, upper and lower back aches, bilateral hip pain, neck pain, headache, night sweats, chills, and nausea. After infectious causes were ruled out, he was placed on a steroid taper without improvement. He presented to the emergency department a few days later with muscle spasms and was found to also have diffuse abdominal tenderness and guarding. The patient’s medical history was noncontributory; he was a lifelong nonsmoker. Laboratory studies revealed elevated levels of alanine aminotransferase and C-reactive protein. Computed tomography of the chest and abdomen revealed innumerable liver and lung lesions that were suspicious for metastatic malignancy. A liver biopsy revealed nests and sheets of metastatic tumor with pleomorphic nuclei, inconspicuous nucleoli, and areas of intranuclear clearing (Figures 1 and 2). Immunohistochemical staining was performed to further characterize the tumor. Neoplastic cells were positive for MART-1 (also known as Melan-A and melanoma-associated antigen recognized by T cells)(Figure 3), SOX10, S-100, HMB-45, and vimentin. Nonspecific staining with CD56 (Figure 4), a neuroendocrine marker, also was noted; however, the neoplasm was negative for synaptophysin, another neuroendocrine marker. Other markers for which staining was negative included pan-keratin, CD138 (syndecan-1), desmin, placental alkaline phosphatase (PLAP), inhibin, OCT-4, cytokeratin 7, and cytokeratin 20. This staining pattern was compatible with metastatic melanoma with aberrant CD56 expression.

BRAF V600E immunohistochemical staining also was performed and showed strong and diffuse positivity within neoplastic cells. A subsequent positron emission tomography scan revealed widespread metastatic disease involving the lungs, liver, spleen, and bones. The patient did not have a history of an excised skin lesion; no primary cutaneous or mucosal lesions were identified.

The patient was started on targeted therapy with trametinib, a mitogen-activated extracellular signal-related kinase kinase (MEK) inhibitor, and dabrafenib, a BRAF inhibitor. The disease continued to progress; he developed extensive leptomeningeal metastatic disease for which palliative radiation therapy was administered. The patient died 4 months after the initial diagnosis.

More than 90% of melanoma cases are of cutaneous origin; however, 4% to 8% of cases present as a metastatic lesion in the absence of an identified primary lesion,⁴ similar to our patient. The diagnosis of melanoma often is challenging; the tumor can show notable histologic diversity and has the potential to express aberrant immunophenotypes.^1,2 The histologic diversity of melanoma includes a variety of architectural patterns (eg, nests, trabeculae, fascicular, pseudoglandular, pseudopapillary, or pseudorosette patterns), cytomorphologic features, and stromal changes. Cytomorphologic features of melanoma can be large pleomorphic cells; small cells; spindle cells; clear cells; signet-ring cells; and rhabdoid, plasmacytoid, and balloon cells.⁵

Melanoma can mimic carcinoma, sarcoma, lymphoma, benign stromal tumors, plasmacytoma, and germ-cell tumors.⁵ Nuclei can binucleated, multinucleated, or lobated and may contain inclusions or grooves. Stroma may become myxoid or desmoplastic in appearance or rarely show granulomatous inflammation or osteoclastic giant cells.⁵ These variations render the diagnosis of melanoma challenging and ultimately can lead to diagnostic uncertainty.

Melanomas typically express MART-1, HMB-45, S-100, tyrosinase, NK1C3, vimentin, and neuron-specific enolase. However, melanoma is among the many neoplasms that sometimes exhibit aberrant immunoreactivity and differentiation toward nonmelanocytic elements.⁶ The most commonly expressed immunophenotypic aberration is cytokeratin, especially the low-molecular-weight keratin marker CAM5.2.⁵ CAM5.2 positivity also is seen more often in metastatic melanoma. Melanomas rarely express other intermediate filaments, including desmin, neurofilament protein, and glial fibrillary acidic protein; expression of smooth-muscle actin is rare.⁵

Only a few cases of melanoma showing expression of neuroendocrine markers have been reported. However, one study reported synaptophysin positivity in 29% (10/34) of cases of primary and metastatic melanoma, making the stain a relatively common finding.¹

In contrast, expression of CD56 (also known as neural-cell adhesion molecule 1) in melanoma has been reported only rarely. CD56 is a nonspecific neuroendocrine marker that normally is expressed on neurons, glial tissue, skeletal muscle, and natural killer cells. Riddle and Bui⁷ reported a case of metastatic malignant melanoma with focal CD56 positivity and no expression of other neuroendocrine markers, similar to our patient. Suzuki and colleagues⁴ also reported a case of melanoma metastatic to bone marrow that showed CD56 expression in true nonhematologic tumor cells and negative immunoreactivity with synaptophysin and chromogranin A.

It is important to document cases of melanoma that express neuroendocrine markers to prevent an incorrect diagnosis of a neuroendocrine tumor.¹ In some cases, distinguishing amelanotic melanoma from poorly differentiated squamous cell carcinoma, neuroendocrine tumor, and lymphoma can be difficult.⁵

The term neuroendocrine differentiation is reserved for cases of melanoma that show areas of ultrastructural change consistent with a neuroendocrine tumor.² Neuroendocrine differentiation in melanoma is not common; its prognostic significance is unknown.⁸ We do not consider our case to be true neuroendocrine differentiation, as the tumor lacked the morphologic changes of a neuroendocrine tumor. Furthermore, CD56 is a nonspecific neuroendocrine marker, and the tumor was negative for synaptophysin.

Melanoma has the potential to show notable histologic diversity as well as aberrant immunohistochemical staining patterns.^1,2 Our patient had metastatic melanoma with aberrant neuroendocrine expression of CD56, which could have been a potential diagnostic pitfall. Because expression of CD56 in melanoma is rare, it is imperative to recognize this potential aberrant staining pattern to ensure the accurate diagnosis of melanoma and appropriate provision of care.

To the Editor:

Granulomatous dermatitis (GD) has been described as a rare side effect of MEK and BRAF inhibitor use in the treatment of BRAF V600E mutation–positive metastatic melanoma. As the utilization of BRAF and MEK inhibitors increases for the treatment of a variety of cancers, it is essential that clinicians and pathologists recognize GD as a potential cutaneous manifestation. We present the case of a 52-year-old woman who developed GD while being treated with vemurafenib and cobimetinib for BRAF V600E mutation–positive metastatic cholangiocarcinoma.

A 52-year-old White woman presented with faint patches of nonpalpable violaceous mottling that extended distally to proximally from the ankles to the thighs on the medial aspects of both legs. She was diagnosed with cholangiocarcinoma 10 months prior, with metastases to the lung, liver, and sternum. She underwent treatment with gemcitabine and cisplatin therapy. Computed tomography after several treatment cycles revealed progressive disease with multiple pulmonary nodules as well as metastatic intrathoracic and abdominal adenopathy. Treatment with gemcitabine and cisplatin failed to produce a favorable response and was discontinued after 6 treatment cycles.

Genomic testing performed at the time of diagnosis revealed a positive mutation for BRAF V600E. The patient subsequently enrolled in a clinical trial and started treatment with the BRAF inhibitor vemurafenib and the MEK inhibitor cobimetinib. She developed sun sensitivity and multiple sunburns after starting these therapies. The patient tolerated the next few cycles of therapy well with only moderate concerns of dry sensitive skin.

During the sixth cycle of therapy, she presented to dermatology after developing a rash. Over the next 2 weeks, similar lesions appeared on the arms. The patient denied the use of any new lotions, soaps, or other medications. Punch biopsies of the right forearm and right medial thigh revealed nonnecrotizing granulomas in the superficial dermis that extended into the subcutaneous adipose tissue (Figure 1). Surrounding chronic inflammation was scant, and the presence of rare eosinophils was noted (Figure 2). The histiocytes were highlighted by a CD68 immunohistochemical stain. An auramine-O special stain test was negative for acid-fast bacilli, and a Grocott methenamine-silver special stain test for fungal organisms was negative. These findings were consistent with GD. Computed tomography of the chest performed 2 months prior and 1 month after biopsy of the skin lesions revealed no axillary, mediastinal, or hilar lymphadenopathy. The calcium level at the time of skin biopsy was within reference range.

A topical steroid was prescribed; however, it was not utilized by the patient. Within 2 months of onset, the GD lesions resolved with no treatment. The GD lesions did not affect the patient’s enrollment in the clinical trial, and no dose reductions were made. Due to progressive disease with metastases to the brain, the patient eventually discontinued the clinical trial.

BRAF inhibitors are US Food and Drug Administration approved for the treatment of metastatic melanoma to deactivate the serine-threonine kinase BRAF gene mutation, which leads to decreased generation and survival of melanoma cells.^1,2 Vemurafenib, dabrafenib, and encorafenib are the only BRAF inhibitors approved in the United States.³ The most common side effects of vemurafenib include arthralgia, fatigue, rash, and photosensitivity.^1,4 There are 4 MEK inhibitors currently available in the United States: cobimetinib, trametinib, selumetinib and binimetinib. The addition of a MEK inhibitor to BRAF inhibitor therapy has shown increased patient response rates and prolonged survival in 3 phase 3 studies.^5-10

Response rates remain low in the treatment of advanced cholangiocarcinoma with standard chemotherapy. Recent research has explored if targeted therapies at the molecular level would be of benefit.¹¹ Our patient was enrolled in the American Society of Clinical Oncology Targeted Agent and Profiling Utilization Registry (TAPUR) trial, a phase 2, prospective, nonrandomized trial that matches eligible participants to US Food and Drug Administration–approved study medications based on specific data from their molecular testing results.¹² Some of the most common mutations in intrahepatic cholangiocarcinoma include HER2, KRAS, MET, and BRAF.^13-17 Our patient’s molecular test results were positive for a BRAF V600E–positive mutation, and she subsequently started therapy with vemurafenib and cobimetinib. The use of personalized genomic treatment approaches for BRAF V600E mutation–positive cholangiocarcinoma has produced a dramatic patient response to BRAF and MEK inhibitor combination therapies.^11,18-20

Drug-induced GD most likely is caused by vascular insults that lead to deposition of immune complexes in vessels causing inflammation and a consequent granulomatous infiltrate.^21,22 Although cordlike lesions in the subcutaneous tissue on the trunk commonly are reported, the presentation of GD can vary considerably. Other presentations include areas of violaceous or erythematous patches or plaques on the limbs, intertriginous areas, and upper trunk. Diffuse macular erythema or small flesh-colored papules also can be observed.²³

Granulomatous dermatitis secondary to drug reactions can have varying morphologies. The infiltrate often can have an interstitial appearance with the presence of lymphocytes, plasma cells, histiocytes, eosinophils, and multinucleated giant cells.²⁴ These findings can be confused with interstitial granuloma annulare. Other cases, such as in our patient, can have discrete granulomata formation with a sarcoidlike appearance. These naked granulomas lack surrounding inflammation and suggest a differential diagnosis of sarcoidosis and infection. Use of immune checkpoint inhibitors (CIs) and kinase inhibitors has been proven to cause sarcoidosislike reactions.²⁵ The development of granulomatous/sarcoidlike lesions associated with the use of BRAF and MEK inhibitors may clinically and radiographically mimic disease recurrence. An awareness of this type of reaction by clinicians and pathologists is important to ensure appropriate management in patients who develop GD.²⁶

Checkpoint inhibitor–induced GD that remains asymptomatic does not necessarily warrant treatment; however, corticosteroid use and elimination of CI therapies have resolved GD in prior cases. Responsiveness of the cancer to CI therapy and severity of GD symptoms should be considered before discontinuation of a CI trial.²⁵

One case report described complete resolution of a GD eruption without interruption of the scheduled BRAF and MEK inhibitor therapies for the treatment of metastatic melanoma. There was no reported use of a steroidal cream or other topical medication to aid in controlling the eruption.²⁷ The exact mechanism of how GD resolves while continuing therapy is unknown; however, it has been suggested that a GD eruption may be the consequence of a BRAF and MEK inhibitor–mediated immune response against a subclinical area of metastatic melanoma.²⁸ If the immune response successfully eliminates the subclinical tumor, one could postulate that the inflammatory response and granulomatous eruption would resolve. Future studies are necessary to further elucidate the exact mechanisms involved.

There have been several case reports of GD with vemurafenib treatment,^29,30 1 report of GD and erythema induratum with vemurafenib and cobimetinib treatment,³¹ 2 reports of GD with dabrafenib treatment,^27,30 and a few reports of GD with the BRAF inhibitor dabrafenib combined with the MEK inhibitor trametinib,^28,32,33 all for the treatment of metastatic melanoma. Additionally, a report described a 3-year-old boy who developed GD secondary to vemurafenib for the treatment of Langerhans cell histiocytosis.³⁴ We present a unique case of BRAF and MEK inhibitor therapy–induced GD in the treatment of metastatic cholangiocarcinoma with vemurafenib and cobimetinib.

BRAF and MEK inhibitor therapy is used in patients with metastatic melanomas with a positive BRAF V600E mutation. Due to advancements in next-generation DNA sequencing, these therapies also are being tested in clinical trials for use in the treatment of other cancers with the same checkpoint mutation, such as metastatic cholangiocarcinoma. Cutaneous reactions frequently are documented side effects that occur during treatment with BRAF and MEK inhibitors; GD is an uncommon finding. As the utilization of BRAF and MEK inhibitors increases for the treatment of a variety of other cancers, it is essential that clinicians and pathologists recognize GD as a potential cutaneous manifestation.

To the Editor:

Granulomatous dermatitis (GD) has been described as a rare side effect of MEK and BRAF inhibitor use in the treatment of BRAF V600E mutation–positive metastatic melanoma. As the utilization of BRAF and MEK inhibitors increases for the treatment of a variety of cancers, it is essential that clinicians and pathologists recognize GD as a potential cutaneous manifestation. We present the case of a 52-year-old woman who developed GD while being treated with vemurafenib and cobimetinib for BRAF V600E mutation–positive metastatic cholangiocarcinoma.

A 52-year-old White woman presented with faint patches of nonpalpable violaceous mottling that extended distally to proximally from the ankles to the thighs on the medial aspects of both legs. She was diagnosed with cholangiocarcinoma 10 months prior, with metastases to the lung, liver, and sternum. She underwent treatment with gemcitabine and cisplatin therapy. Computed tomography after several treatment cycles revealed progressive disease with multiple pulmonary nodules as well as metastatic intrathoracic and abdominal adenopathy. Treatment with gemcitabine and cisplatin failed to produce a favorable response and was discontinued after 6 treatment cycles.

Genomic testing performed at the time of diagnosis revealed a positive mutation for BRAF V600E. The patient subsequently enrolled in a clinical trial and started treatment with the BRAF inhibitor vemurafenib and the MEK inhibitor cobimetinib. She developed sun sensitivity and multiple sunburns after starting these therapies. The patient tolerated the next few cycles of therapy well with only moderate concerns of dry sensitive skin.

During the sixth cycle of therapy, she presented to dermatology after developing a rash. Over the next 2 weeks, similar lesions appeared on the arms. The patient denied the use of any new lotions, soaps, or other medications. Punch biopsies of the right forearm and right medial thigh revealed nonnecrotizing granulomas in the superficial dermis that extended into the subcutaneous adipose tissue (Figure 1). Surrounding chronic inflammation was scant, and the presence of rare eosinophils was noted (Figure 2). The histiocytes were highlighted by a CD68 immunohistochemical stain. An auramine-O special stain test was negative for acid-fast bacilli, and a Grocott methenamine-silver special stain test for fungal organisms was negative. These findings were consistent with GD. Computed tomography of the chest performed 2 months prior and 1 month after biopsy of the skin lesions revealed no axillary, mediastinal, or hilar lymphadenopathy. The calcium level at the time of skin biopsy was within reference range.

A topical steroid was prescribed; however, it was not utilized by the patient. Within 2 months of onset, the GD lesions resolved with no treatment. The GD lesions did not affect the patient’s enrollment in the clinical trial, and no dose reductions were made. Due to progressive disease with metastases to the brain, the patient eventually discontinued the clinical trial.

BRAF inhibitors are US Food and Drug Administration approved for the treatment of metastatic melanoma to deactivate the serine-threonine kinase BRAF gene mutation, which leads to decreased generation and survival of melanoma cells.^1,2 Vemurafenib, dabrafenib, and encorafenib are the only BRAF inhibitors approved in the United States.³ The most common side effects of vemurafenib include arthralgia, fatigue, rash, and photosensitivity.^1,4 There are 4 MEK inhibitors currently available in the United States: cobimetinib, trametinib, selumetinib and binimetinib. The addition of a MEK inhibitor to BRAF inhibitor therapy has shown increased patient response rates and prolonged survival in 3 phase 3 studies.^5-10

Response rates remain low in the treatment of advanced cholangiocarcinoma with standard chemotherapy. Recent research has explored if targeted therapies at the molecular level would be of benefit.¹¹ Our patient was enrolled in the American Society of Clinical Oncology Targeted Agent and Profiling Utilization Registry (TAPUR) trial, a phase 2, prospective, nonrandomized trial that matches eligible participants to US Food and Drug Administration–approved study medications based on specific data from their molecular testing results.¹² Some of the most common mutations in intrahepatic cholangiocarcinoma include HER2, KRAS, MET, and BRAF.^13-17 Our patient’s molecular test results were positive for a BRAF V600E–positive mutation, and she subsequently started therapy with vemurafenib and cobimetinib. The use of personalized genomic treatment approaches for BRAF V600E mutation–positive cholangiocarcinoma has produced a dramatic patient response to BRAF and MEK inhibitor combination therapies.^11,18-20

Drug-induced GD most likely is caused by vascular insults that lead to deposition of immune complexes in vessels causing inflammation and a consequent granulomatous infiltrate.^21,22 Although cordlike lesions in the subcutaneous tissue on the trunk commonly are reported, the presentation of GD can vary considerably. Other presentations include areas of violaceous or erythematous patches or plaques on the limbs, intertriginous areas, and upper trunk. Diffuse macular erythema or small flesh-colored papules also can be observed.²³

Granulomatous dermatitis secondary to drug reactions can have varying morphologies. The infiltrate often can have an interstitial appearance with the presence of lymphocytes, plasma cells, histiocytes, eosinophils, and multinucleated giant cells.²⁴ These findings can be confused with interstitial granuloma annulare. Other cases, such as in our patient, can have discrete granulomata formation with a sarcoidlike appearance. These naked granulomas lack surrounding inflammation and suggest a differential diagnosis of sarcoidosis and infection. Use of immune checkpoint inhibitors (CIs) and kinase inhibitors has been proven to cause sarcoidosislike reactions.²⁵ The development of granulomatous/sarcoidlike lesions associated with the use of BRAF and MEK inhibitors may clinically and radiographically mimic disease recurrence. An awareness of this type of reaction by clinicians and pathologists is important to ensure appropriate management in patients who develop GD.²⁶

Checkpoint inhibitor–induced GD that remains asymptomatic does not necessarily warrant treatment; however, corticosteroid use and elimination of CI therapies have resolved GD in prior cases. Responsiveness of the cancer to CI therapy and severity of GD symptoms should be considered before discontinuation of a CI trial.²⁵

One case report described complete resolution of a GD eruption without interruption of the scheduled BRAF and MEK inhibitor therapies for the treatment of metastatic melanoma. There was no reported use of a steroidal cream or other topical medication to aid in controlling the eruption.²⁷ The exact mechanism of how GD resolves while continuing therapy is unknown; however, it has been suggested that a GD eruption may be the consequence of a BRAF and MEK inhibitor–mediated immune response against a subclinical area of metastatic melanoma.²⁸ If the immune response successfully eliminates the subclinical tumor, one could postulate that the inflammatory response and granulomatous eruption would resolve. Future studies are necessary to further elucidate the exact mechanisms involved.

There have been several case reports of GD with vemurafenib treatment,^29,30 1 report of GD and erythema induratum with vemurafenib and cobimetinib treatment,³¹ 2 reports of GD with dabrafenib treatment,^27,30 and a few reports of GD with the BRAF inhibitor dabrafenib combined with the MEK inhibitor trametinib,^28,32,33 all for the treatment of metastatic melanoma. Additionally, a report described a 3-year-old boy who developed GD secondary to vemurafenib for the treatment of Langerhans cell histiocytosis.³⁴ We present a unique case of BRAF and MEK inhibitor therapy–induced GD in the treatment of metastatic cholangiocarcinoma with vemurafenib and cobimetinib.

BRAF and MEK inhibitor therapy is used in patients with metastatic melanomas with a positive BRAF V600E mutation. Due to advancements in next-generation DNA sequencing, these therapies also are being tested in clinical trials for use in the treatment of other cancers with the same checkpoint mutation, such as metastatic cholangiocarcinoma. Cutaneous reactions frequently are documented side effects that occur during treatment with BRAF and MEK inhibitors; GD is an uncommon finding. As the utilization of BRAF and MEK inhibitors increases for the treatment of a variety of other cancers, it is essential that clinicians and pathologists recognize GD as a potential cutaneous manifestation.

To the Editor:

Granulomatous dermatitis (GD) has been described as a rare side effect of MEK and BRAF inhibitor use in the treatment of BRAF V600E mutation–positive metastatic melanoma. As the utilization of BRAF and MEK inhibitors increases for the treatment of a variety of cancers, it is essential that clinicians and pathologists recognize GD as a potential cutaneous manifestation. We present the case of a 52-year-old woman who developed GD while being treated with vemurafenib and cobimetinib for BRAF V600E mutation–positive metastatic cholangiocarcinoma.

A 52-year-old White woman presented with faint patches of nonpalpable violaceous mottling that extended distally to proximally from the ankles to the thighs on the medial aspects of both legs. She was diagnosed with cholangiocarcinoma 10 months prior, with metastases to the lung, liver, and sternum. She underwent treatment with gemcitabine and cisplatin therapy. Computed tomography after several treatment cycles revealed progressive disease with multiple pulmonary nodules as well as metastatic intrathoracic and abdominal adenopathy. Treatment with gemcitabine and cisplatin failed to produce a favorable response and was discontinued after 6 treatment cycles.

Genomic testing performed at the time of diagnosis revealed a positive mutation for BRAF V600E. The patient subsequently enrolled in a clinical trial and started treatment with the BRAF inhibitor vemurafenib and the MEK inhibitor cobimetinib. She developed sun sensitivity and multiple sunburns after starting these therapies. The patient tolerated the next few cycles of therapy well with only moderate concerns of dry sensitive skin.

During the sixth cycle of therapy, she presented to dermatology after developing a rash. Over the next 2 weeks, similar lesions appeared on the arms. The patient denied the use of any new lotions, soaps, or other medications. Punch biopsies of the right forearm and right medial thigh revealed nonnecrotizing granulomas in the superficial dermis that extended into the subcutaneous adipose tissue (Figure 1). Surrounding chronic inflammation was scant, and the presence of rare eosinophils was noted (Figure 2). The histiocytes were highlighted by a CD68 immunohistochemical stain. An auramine-O special stain test was negative for acid-fast bacilli, and a Grocott methenamine-silver special stain test for fungal organisms was negative. These findings were consistent with GD. Computed tomography of the chest performed 2 months prior and 1 month after biopsy of the skin lesions revealed no axillary, mediastinal, or hilar lymphadenopathy. The calcium level at the time of skin biopsy was within reference range.

A topical steroid was prescribed; however, it was not utilized by the patient. Within 2 months of onset, the GD lesions resolved with no treatment. The GD lesions did not affect the patient’s enrollment in the clinical trial, and no dose reductions were made. Due to progressive disease with metastases to the brain, the patient eventually discontinued the clinical trial.

BRAF inhibitors are US Food and Drug Administration approved for the treatment of metastatic melanoma to deactivate the serine-threonine kinase BRAF gene mutation, which leads to decreased generation and survival of melanoma cells.^1,2 Vemurafenib, dabrafenib, and encorafenib are the only BRAF inhibitors approved in the United States.³ The most common side effects of vemurafenib include arthralgia, fatigue, rash, and photosensitivity.^1,4 There are 4 MEK inhibitors currently available in the United States: cobimetinib, trametinib, selumetinib and binimetinib. The addition of a MEK inhibitor to BRAF inhibitor therapy has shown increased patient response rates and prolonged survival in 3 phase 3 studies.^5-10

Response rates remain low in the treatment of advanced cholangiocarcinoma with standard chemotherapy. Recent research has explored if targeted therapies at the molecular level would be of benefit.¹¹ Our patient was enrolled in the American Society of Clinical Oncology Targeted Agent and Profiling Utilization Registry (TAPUR) trial, a phase 2, prospective, nonrandomized trial that matches eligible participants to US Food and Drug Administration–approved study medications based on specific data from their molecular testing results.¹² Some of the most common mutations in intrahepatic cholangiocarcinoma include HER2, KRAS, MET, and BRAF.^13-17 Our patient’s molecular test results were positive for a BRAF V600E–positive mutation, and she subsequently started therapy with vemurafenib and cobimetinib. The use of personalized genomic treatment approaches for BRAF V600E mutation–positive cholangiocarcinoma has produced a dramatic patient response to BRAF and MEK inhibitor combination therapies.^11,18-20

Drug-induced GD most likely is caused by vascular insults that lead to deposition of immune complexes in vessels causing inflammation and a consequent granulomatous infiltrate.^21,22 Although cordlike lesions in the subcutaneous tissue on the trunk commonly are reported, the presentation of GD can vary considerably. Other presentations include areas of violaceous or erythematous patches or plaques on the limbs, intertriginous areas, and upper trunk. Diffuse macular erythema or small flesh-colored papules also can be observed.²³

Granulomatous dermatitis secondary to drug reactions can have varying morphologies. The infiltrate often can have an interstitial appearance with the presence of lymphocytes, plasma cells, histiocytes, eosinophils, and multinucleated giant cells.²⁴ These findings can be confused with interstitial granuloma annulare. Other cases, such as in our patient, can have discrete granulomata formation with a sarcoidlike appearance. These naked granulomas lack surrounding inflammation and suggest a differential diagnosis of sarcoidosis and infection. Use of immune checkpoint inhibitors (CIs) and kinase inhibitors has been proven to cause sarcoidosislike reactions.²⁵ The development of granulomatous/sarcoidlike lesions associated with the use of BRAF and MEK inhibitors may clinically and radiographically mimic disease recurrence. An awareness of this type of reaction by clinicians and pathologists is important to ensure appropriate management in patients who develop GD.²⁶

Checkpoint inhibitor–induced GD that remains asymptomatic does not necessarily warrant treatment; however, corticosteroid use and elimination of CI therapies have resolved GD in prior cases. Responsiveness of the cancer to CI therapy and severity of GD symptoms should be considered before discontinuation of a CI trial.²⁵

One case report described complete resolution of a GD eruption without interruption of the scheduled BRAF and MEK inhibitor therapies for the treatment of metastatic melanoma. There was no reported use of a steroidal cream or other topical medication to aid in controlling the eruption.²⁷ The exact mechanism of how GD resolves while continuing therapy is unknown; however, it has been suggested that a GD eruption may be the consequence of a BRAF and MEK inhibitor–mediated immune response against a subclinical area of metastatic melanoma.²⁸ If the immune response successfully eliminates the subclinical tumor, one could postulate that the inflammatory response and granulomatous eruption would resolve. Future studies are necessary to further elucidate the exact mechanisms involved.

There have been several case reports of GD with vemurafenib treatment,^29,30 1 report of GD and erythema induratum with vemurafenib and cobimetinib treatment,³¹ 2 reports of GD with dabrafenib treatment,^27,30 and a few reports of GD with the BRAF inhibitor dabrafenib combined with the MEK inhibitor trametinib,^28,32,33 all for the treatment of metastatic melanoma. Additionally, a report described a 3-year-old boy who developed GD secondary to vemurafenib for the treatment of Langerhans cell histiocytosis.³⁴ We present a unique case of BRAF and MEK inhibitor therapy–induced GD in the treatment of metastatic cholangiocarcinoma with vemurafenib and cobimetinib.

BRAF and MEK inhibitor therapy is used in patients with metastatic melanomas with a positive BRAF V600E mutation. Due to advancements in next-generation DNA sequencing, these therapies also are being tested in clinical trials for use in the treatment of other cancers with the same checkpoint mutation, such as metastatic cholangiocarcinoma. Cutaneous reactions frequently are documented side effects that occur during treatment with BRAF and MEK inhibitors; GD is an uncommon finding. As the utilization of BRAF and MEK inhibitors increases for the treatment of a variety of other cancers, it is essential that clinicians and pathologists recognize GD as a potential cutaneous manifestation.

Case Report

A 79-year-old man with chronic lymphocytic leukemia (CLL) who was being treated with ibrutinib presented to the emergency department with a dry cough, ataxia and falls, and vision loss. Physical examination was remarkable for diffuse crackles heard throughout the right lung and bilateral lower extremity weakness. Additionally, he had 4 pink mobile nodules on the left side of the forehead, right side of the chin, left submental area, and left postauricular scalp, which arose approximately 2 weeks prior to presentation. The left postauricular lesion had been tender at times and had developed a crust. The cutaneous lesions were all smaller than 2 cm.

The patient had a history of squamous cell carcinoma of the skin and was under the care of a dermatologist as an outpatient. His dermatologist had described him as an active gardener; he was noted to have healing abrasions on the forearms due to gardening raspberry bushes.

Computed tomography of the head revealed a 14-mm, ring-enhancing lesion in the left paramedian posterior frontal lobe with surrounding white matter vasogenic edema (Figure 1). Computed tomography of the chest revealed a peripheral mass on the right upper lobe measuring 6.3 cm at its greatest dimension (Figure 2).

Clinically, the constellation of symptoms was thought to represent an infectious process or less likely metastatic malignancy. Biopsies of the nodule on the right side of the chin were performed and sent for culture and histologic examination. Sections from the anterior right chin showed compact orthokeratosis overlying a slightly spongiotic epidermis (Figure 3). Within the deep dermis, there was a dense mixed inflammatory infiltrate comprising predominantly neutrophils, with occasional eosinophils, lymphocytes, and histiocytes (Figure 4).

Gram stain revealed gram-variable, branching, bacterial organisms morphologically consistent with Nocardia. Grocott-Gomori methenamine-silver and periodic acid–Schiff stains also highlighted the bacterial organisms (Figure 5). An auramine-O stain was negative for acid-fast microorganisms. After 3 days on a blood agar plate, cultures of a specimen of the chin nodule grew branching filamentous bacterial organisms consistent with Nocardia.

Comment

Presentation and Diagnosis
Nocardiosis is an infrequently encountered opportunistic infection that typically targets skin, lungs, and the central nervous system (CNS). Nocardia species characteristically are gram-positive, thin rods that form beaded, right-angle, branching filaments.¹ More than 50 Nocardia species have been clinically isolated.²

Definitive diagnosis requires culture. Nocardia grows well on nonselective media, such as blood or Löwenstein-Jensen agar; growth can be enhanced with 10% CO₂. Growth can be slow, however, and takes from 48 hours to several weeks. Nocardia typically grows as buff or pigmented, waxy, cerebriform colonies at 3 to 5 days’ incubation.¹

Cause of Infection
Nocardia species are commonly found in the environment—soil, plant matter, water, and decomposing organic material—as well as in the gastrointestinal tract and skin of animals. Infection has been reported in cattle, dogs, horses, swine, birds, cats, foxes, and a few other animals.² A history of exposure, such as gardening or handling animals, should increase suspicion of Nocardia.³ Although infection is classically thought to affect immunocompromised patients, there are case reports of immunocompetent individuals developing disseminated infection.^4-7 However, infected immunocompetent individuals typically have localized cutaneous infection, which often includes cellulitis, abscesses, or sporotrichoid patterns.² Cutaneous infections typically are the result of direct inoculation of the skin through a penetrating injury.⁸

Disseminated nocardiosis can be caused by numerous species and generally is the result of primary pulmonary infection.⁹ In these cases, skin disease is present in approximately 10% of patients. Disseminated infection from cutaneous nocardiosis is uncommon; when it does occur, the most common site of dissemination is the CNS, resulting in abscess or cerebritis.¹⁰ Therefore, CNS involvement should always be ruled out on diagnosis in immunocompromised patients, even if neurologic symptoms are absent.⁹ Nearly 80% of patients with disseminated disease are, in fact, immunocompromised.⁸

Association With CLL
Chronic lymphocytic leukemia is associated with profound immunodeficiency caused by quantitative and qualitative aberrations in both innate and adaptive immunity. This perturbation of the immune system predisposes the patient to infection.^11,12 Early in the course of CLL, a patient develops neutropenia, which predisposes to bacterial infection; later, the patient develops a sustained B- and T-cell immunodeficiency that predisposes to opportunistic infection.¹³ Treatment-naïve patients with CLL are commonly diagnosed with respiratory and urinary tract infections.¹² Chronic lymphocytic leukemia patients treated with alemtuzumab or purine analogs have been reported to have the highest risk for major infection.¹⁴

Ibrutinib is a commonly used treatment of CLL because it induces apoptosis in B cells, which are abnormal in CLL. Ibrutinib functions by inhibiting the Bruton tyrosine kinase pathway, which is essential in B-cell production and maintenance.¹⁵ Studies have reported a high rate of infection in ibrutinib-treated CLL patients^14,16; salvage ibrutinib therapy has been associated with higher infection risk than primary ibrutinib therapy.^16,17 Long-term follow-up studies have shown a decreased rate of infection in ibrutinib-treated CLL after 2 years or longer of treatment, suggesting a reconstitution of normal B cells and humoral immunity with longer ibrutinib therapy.^16,17

Many infections have been identified in association with ibrutinib therapy, including invasive aspergillosis, disseminated fusariosis, cerebral mucormycosis, disseminated cryptococcosis, and Pneumocystis jirovecii pneumonia.^18-22 Disseminated nocardiosis has been reported in a few patients with CLL, though the treatment they received for CLL varied from case to case.^23-25

Identification and Treatment
Clinical and microscopic identification of Nocardia organisms can be exceedingly difficult. Primary cutaneous nocardiosis clinically presents as tumors or nodules that often have a sporotrichoid pattern along the lymphatics. In disease that disseminates to skin, nocardiosis presents as vesiculopustules or abscesses. The biopsy specimen most often shows a dense dermal and subcutaneous infiltrate of neutrophils with abscess formation. Long-standing lesions might show chronic inflammation and nonspecific granulomas.

The appearance of Nocardia organisms is quite subtle on hematoxylin and eosin staining and can be easily missed. Special stains, such as Gram and Grocott-Gomori methenamine-silver stains as well as stains for acid-fast organisms, can be invaluable in diagnosing this disease. Biopsy in immunocompromised patients when nocardiosis is part of the differential diagnosis requires extra attention because the organisms can be gram variable and only partially acid fast, as was the case in our patient. Organisms typically will be positive with silver stains.

Trimethoprim-sulfamethoxazole typically is the first-line treatment of nocardiosis. Although prognosis is excellent when disease is confined to skin, disseminated infection has 25% mortality.⁸ Diagnosticians should maintain a high index of suspicion for the disease, especially in immunocompromised patients, because clinical and imaging findings can be nonspecific.

Conclusion

Our patient’s primary risk factor for nocardiosis was his immunocompromised state. In addition, he was an avid gardener, which increased his risk for exposure to the microorganism. Given the timing of disease progression, our case most likely represents primary cutaneous nocardiosis with dissemination to brain, lungs, and other organs, leading to death, and serves as a reminder to dermatologists and pathologists to establish a broad differential diagnosis when dealing with an infectious process in immunocompromised patients.

Case Report

A 79-year-old man with chronic lymphocytic leukemia (CLL) who was being treated with ibrutinib presented to the emergency department with a dry cough, ataxia and falls, and vision loss. Physical examination was remarkable for diffuse crackles heard throughout the right lung and bilateral lower extremity weakness. Additionally, he had 4 pink mobile nodules on the left side of the forehead, right side of the chin, left submental area, and left postauricular scalp, which arose approximately 2 weeks prior to presentation. The left postauricular lesion had been tender at times and had developed a crust. The cutaneous lesions were all smaller than 2 cm.

The patient had a history of squamous cell carcinoma of the skin and was under the care of a dermatologist as an outpatient. His dermatologist had described him as an active gardener; he was noted to have healing abrasions on the forearms due to gardening raspberry bushes.

Computed tomography of the head revealed a 14-mm, ring-enhancing lesion in the left paramedian posterior frontal lobe with surrounding white matter vasogenic edema (Figure 1). Computed tomography of the chest revealed a peripheral mass on the right upper lobe measuring 6.3 cm at its greatest dimension (Figure 2).

Clinically, the constellation of symptoms was thought to represent an infectious process or less likely metastatic malignancy. Biopsies of the nodule on the right side of the chin were performed and sent for culture and histologic examination. Sections from the anterior right chin showed compact orthokeratosis overlying a slightly spongiotic epidermis (Figure 3). Within the deep dermis, there was a dense mixed inflammatory infiltrate comprising predominantly neutrophils, with occasional eosinophils, lymphocytes, and histiocytes (Figure 4).

Gram stain revealed gram-variable, branching, bacterial organisms morphologically consistent with Nocardia. Grocott-Gomori methenamine-silver and periodic acid–Schiff stains also highlighted the bacterial organisms (Figure 5). An auramine-O stain was negative for acid-fast microorganisms. After 3 days on a blood agar plate, cultures of a specimen of the chin nodule grew branching filamentous bacterial organisms consistent with Nocardia.

Comment

Presentation and Diagnosis
Nocardiosis is an infrequently encountered opportunistic infection that typically targets skin, lungs, and the central nervous system (CNS). Nocardia species characteristically are gram-positive, thin rods that form beaded, right-angle, branching filaments.¹ More than 50 Nocardia species have been clinically isolated.²

Definitive diagnosis requires culture. Nocardia grows well on nonselective media, such as blood or Löwenstein-Jensen agar; growth can be enhanced with 10% CO₂. Growth can be slow, however, and takes from 48 hours to several weeks. Nocardia typically grows as buff or pigmented, waxy, cerebriform colonies at 3 to 5 days’ incubation.¹

Cause of Infection
Nocardia species are commonly found in the environment—soil, plant matter, water, and decomposing organic material—as well as in the gastrointestinal tract and skin of animals. Infection has been reported in cattle, dogs, horses, swine, birds, cats, foxes, and a few other animals.² A history of exposure, such as gardening or handling animals, should increase suspicion of Nocardia.³ Although infection is classically thought to affect immunocompromised patients, there are case reports of immunocompetent individuals developing disseminated infection.^4-7 However, infected immunocompetent individuals typically have localized cutaneous infection, which often includes cellulitis, abscesses, or sporotrichoid patterns.² Cutaneous infections typically are the result of direct inoculation of the skin through a penetrating injury.⁸

Disseminated nocardiosis can be caused by numerous species and generally is the result of primary pulmonary infection.⁹ In these cases, skin disease is present in approximately 10% of patients. Disseminated infection from cutaneous nocardiosis is uncommon; when it does occur, the most common site of dissemination is the CNS, resulting in abscess or cerebritis.¹⁰ Therefore, CNS involvement should always be ruled out on diagnosis in immunocompromised patients, even if neurologic symptoms are absent.⁹ Nearly 80% of patients with disseminated disease are, in fact, immunocompromised.⁸

Association With CLL
Chronic lymphocytic leukemia is associated with profound immunodeficiency caused by quantitative and qualitative aberrations in both innate and adaptive immunity. This perturbation of the immune system predisposes the patient to infection.^11,12 Early in the course of CLL, a patient develops neutropenia, which predisposes to bacterial infection; later, the patient develops a sustained B- and T-cell immunodeficiency that predisposes to opportunistic infection.¹³ Treatment-naïve patients with CLL are commonly diagnosed with respiratory and urinary tract infections.¹² Chronic lymphocytic leukemia patients treated with alemtuzumab or purine analogs have been reported to have the highest risk for major infection.¹⁴

Ibrutinib is a commonly used treatment of CLL because it induces apoptosis in B cells, which are abnormal in CLL. Ibrutinib functions by inhibiting the Bruton tyrosine kinase pathway, which is essential in B-cell production and maintenance.¹⁵ Studies have reported a high rate of infection in ibrutinib-treated CLL patients^14,16; salvage ibrutinib therapy has been associated with higher infection risk than primary ibrutinib therapy.^16,17 Long-term follow-up studies have shown a decreased rate of infection in ibrutinib-treated CLL after 2 years or longer of treatment, suggesting a reconstitution of normal B cells and humoral immunity with longer ibrutinib therapy.^16,17

Many infections have been identified in association with ibrutinib therapy, including invasive aspergillosis, disseminated fusariosis, cerebral mucormycosis, disseminated cryptococcosis, and Pneumocystis jirovecii pneumonia.^18-22 Disseminated nocardiosis has been reported in a few patients with CLL, though the treatment they received for CLL varied from case to case.^23-25

Identification and Treatment
Clinical and microscopic identification of Nocardia organisms can be exceedingly difficult. Primary cutaneous nocardiosis clinically presents as tumors or nodules that often have a sporotrichoid pattern along the lymphatics. In disease that disseminates to skin, nocardiosis presents as vesiculopustules or abscesses. The biopsy specimen most often shows a dense dermal and subcutaneous infiltrate of neutrophils with abscess formation. Long-standing lesions might show chronic inflammation and nonspecific granulomas.

The appearance of Nocardia organisms is quite subtle on hematoxylin and eosin staining and can be easily missed. Special stains, such as Gram and Grocott-Gomori methenamine-silver stains as well as stains for acid-fast organisms, can be invaluable in diagnosing this disease. Biopsy in immunocompromised patients when nocardiosis is part of the differential diagnosis requires extra attention because the organisms can be gram variable and only partially acid fast, as was the case in our patient. Organisms typically will be positive with silver stains.

Trimethoprim-sulfamethoxazole typically is the first-line treatment of nocardiosis. Although prognosis is excellent when disease is confined to skin, disseminated infection has 25% mortality.⁸ Diagnosticians should maintain a high index of suspicion for the disease, especially in immunocompromised patients, because clinical and imaging findings can be nonspecific.

Conclusion

Our patient’s primary risk factor for nocardiosis was his immunocompromised state. In addition, he was an avid gardener, which increased his risk for exposure to the microorganism. Given the timing of disease progression, our case most likely represents primary cutaneous nocardiosis with dissemination to brain, lungs, and other organs, leading to death, and serves as a reminder to dermatologists and pathologists to establish a broad differential diagnosis when dealing with an infectious process in immunocompromised patients.

Case Report

A 79-year-old man with chronic lymphocytic leukemia (CLL) who was being treated with ibrutinib presented to the emergency department with a dry cough, ataxia and falls, and vision loss. Physical examination was remarkable for diffuse crackles heard throughout the right lung and bilateral lower extremity weakness. Additionally, he had 4 pink mobile nodules on the left side of the forehead, right side of the chin, left submental area, and left postauricular scalp, which arose approximately 2 weeks prior to presentation. The left postauricular lesion had been tender at times and had developed a crust. The cutaneous lesions were all smaller than 2 cm.

The patient had a history of squamous cell carcinoma of the skin and was under the care of a dermatologist as an outpatient. His dermatologist had described him as an active gardener; he was noted to have healing abrasions on the forearms due to gardening raspberry bushes.

Computed tomography of the head revealed a 14-mm, ring-enhancing lesion in the left paramedian posterior frontal lobe with surrounding white matter vasogenic edema (Figure 1). Computed tomography of the chest revealed a peripheral mass on the right upper lobe measuring 6.3 cm at its greatest dimension (Figure 2).

Clinically, the constellation of symptoms was thought to represent an infectious process or less likely metastatic malignancy. Biopsies of the nodule on the right side of the chin were performed and sent for culture and histologic examination. Sections from the anterior right chin showed compact orthokeratosis overlying a slightly spongiotic epidermis (Figure 3). Within the deep dermis, there was a dense mixed inflammatory infiltrate comprising predominantly neutrophils, with occasional eosinophils, lymphocytes, and histiocytes (Figure 4).

Gram stain revealed gram-variable, branching, bacterial organisms morphologically consistent with Nocardia. Grocott-Gomori methenamine-silver and periodic acid–Schiff stains also highlighted the bacterial organisms (Figure 5). An auramine-O stain was negative for acid-fast microorganisms. After 3 days on a blood agar plate, cultures of a specimen of the chin nodule grew branching filamentous bacterial organisms consistent with Nocardia.

Comment

Presentation and Diagnosis
Nocardiosis is an infrequently encountered opportunistic infection that typically targets skin, lungs, and the central nervous system (CNS). Nocardia species characteristically are gram-positive, thin rods that form beaded, right-angle, branching filaments.¹ More than 50 Nocardia species have been clinically isolated.²

Definitive diagnosis requires culture. Nocardia grows well on nonselective media, such as blood or Löwenstein-Jensen agar; growth can be enhanced with 10% CO₂. Growth can be slow, however, and takes from 48 hours to several weeks. Nocardia typically grows as buff or pigmented, waxy, cerebriform colonies at 3 to 5 days’ incubation.¹

Cause of Infection
Nocardia species are commonly found in the environment—soil, plant matter, water, and decomposing organic material—as well as in the gastrointestinal tract and skin of animals. Infection has been reported in cattle, dogs, horses, swine, birds, cats, foxes, and a few other animals.² A history of exposure, such as gardening or handling animals, should increase suspicion of Nocardia.³ Although infection is classically thought to affect immunocompromised patients, there are case reports of immunocompetent individuals developing disseminated infection.^4-7 However, infected immunocompetent individuals typically have localized cutaneous infection, which often includes cellulitis, abscesses, or sporotrichoid patterns.² Cutaneous infections typically are the result of direct inoculation of the skin through a penetrating injury.⁸

Disseminated nocardiosis can be caused by numerous species and generally is the result of primary pulmonary infection.⁹ In these cases, skin disease is present in approximately 10% of patients. Disseminated infection from cutaneous nocardiosis is uncommon; when it does occur, the most common site of dissemination is the CNS, resulting in abscess or cerebritis.¹⁰ Therefore, CNS involvement should always be ruled out on diagnosis in immunocompromised patients, even if neurologic symptoms are absent.⁹ Nearly 80% of patients with disseminated disease are, in fact, immunocompromised.⁸

Association With CLL
Chronic lymphocytic leukemia is associated with profound immunodeficiency caused by quantitative and qualitative aberrations in both innate and adaptive immunity. This perturbation of the immune system predisposes the patient to infection.^11,12 Early in the course of CLL, a patient develops neutropenia, which predisposes to bacterial infection; later, the patient develops a sustained B- and T-cell immunodeficiency that predisposes to opportunistic infection.¹³ Treatment-naïve patients with CLL are commonly diagnosed with respiratory and urinary tract infections.¹² Chronic lymphocytic leukemia patients treated with alemtuzumab or purine analogs have been reported to have the highest risk for major infection.¹⁴

Ibrutinib is a commonly used treatment of CLL because it induces apoptosis in B cells, which are abnormal in CLL. Ibrutinib functions by inhibiting the Bruton tyrosine kinase pathway, which is essential in B-cell production and maintenance.¹⁵ Studies have reported a high rate of infection in ibrutinib-treated CLL patients^14,16; salvage ibrutinib therapy has been associated with higher infection risk than primary ibrutinib therapy.^16,17 Long-term follow-up studies have shown a decreased rate of infection in ibrutinib-treated CLL after 2 years or longer of treatment, suggesting a reconstitution of normal B cells and humoral immunity with longer ibrutinib therapy.^16,17

Many infections have been identified in association with ibrutinib therapy, including invasive aspergillosis, disseminated fusariosis, cerebral mucormycosis, disseminated cryptococcosis, and Pneumocystis jirovecii pneumonia.^18-22 Disseminated nocardiosis has been reported in a few patients with CLL, though the treatment they received for CLL varied from case to case.^23-25

Identification and Treatment
Clinical and microscopic identification of Nocardia organisms can be exceedingly difficult. Primary cutaneous nocardiosis clinically presents as tumors or nodules that often have a sporotrichoid pattern along the lymphatics. In disease that disseminates to skin, nocardiosis presents as vesiculopustules or abscesses. The biopsy specimen most often shows a dense dermal and subcutaneous infiltrate of neutrophils with abscess formation. Long-standing lesions might show chronic inflammation and nonspecific granulomas.

The appearance of Nocardia organisms is quite subtle on hematoxylin and eosin staining and can be easily missed. Special stains, such as Gram and Grocott-Gomori methenamine-silver stains as well as stains for acid-fast organisms, can be invaluable in diagnosing this disease. Biopsy in immunocompromised patients when nocardiosis is part of the differential diagnosis requires extra attention because the organisms can be gram variable and only partially acid fast, as was the case in our patient. Organisms typically will be positive with silver stains.

Trimethoprim-sulfamethoxazole typically is the first-line treatment of nocardiosis. Although prognosis is excellent when disease is confined to skin, disseminated infection has 25% mortality.⁸ Diagnosticians should maintain a high index of suspicion for the disease, especially in immunocompromised patients, because clinical and imaging findings can be nonspecific.

Conclusion

Our patient’s primary risk factor for nocardiosis was his immunocompromised state. In addition, he was an avid gardener, which increased his risk for exposure to the microorganism. Given the timing of disease progression, our case most likely represents primary cutaneous nocardiosis with dissemination to brain, lungs, and other organs, leading to death, and serves as a reminder to dermatologists and pathologists to establish a broad differential diagnosis when dealing with an infectious process in immunocompromised patients.