Sean Branch, DO

To the Editor:

The concept of field cancerization has been well described since its initial proposal by Slaughter et al¹ in 1953. It describes a field of genetically altered cells where multiple clonally related neoplasms can develop.^2,3 Treatment of patients with multiple neoplasms within an area of field cancerization can be especially challenging. We report a patient with field cancerization who had multiple squamous cell carcinomas (SCCs) and keratoacanthomas (KAs) that arose within the field.

A 78-year-old man initially presented with a papule on the right forearm of 3 months’ duration. He had a medical history of cutaneous SCC, myocardial infarction, type 2 diabetes mellitus, chronic obstructive pulmonary disease, hypertension, hypercholesterolemia, gout, and diverticulosis. He was not taking any chronic immunosuppressants that may have predisposed him to the development of nonmelanoma skin cancer. The papule was biopsied and diagnosed as a well-differentiated invasive SCC. A month later it was excised with clear margins.

Approximately 5 weeks after the excision, he returned with an enlarging lesion on the right forearm just medial to the excision site. The lesion was biopsied and diagnosed as a well-differentiated SCC. Two months later the lesion was excised with clear margins. Four weeks later he returned with a new lesion adjacent to the medial aspect of the prior excision. The lesion was biopsied and diagnosed as a well-differentiated SCC. Four weeks later the lesion was excised with clear margins.

Another 4 weeks later the patient returned with a new lesion on the excision site. The lesion was biopsied and diagnosed as a well-differentiated SCC. The lesion was treated with radiotherapy, with a 5800-cGy course completed 2 months later. The next month, 2 papules just adjacent to the radiotherapy treatment field were biopsied and diagnosed as well-differentiated SCC, KA type. One week later, 2 additional new papules adjacent to the radiotherapy treatment field were biopsied and diagnosed as moderately differentiated SCC, KA type. At this time, the patient had 4 biopsy-proven KAs on the right forearm in the area of prior radiation (Figure, A). The radiation oncologist felt that further radiation was no longer indicated. A consultation was sought with surgical oncology, and wide excision of the field with sentinel lymph node biopsy and skin grafting was recommended. Computed tomography with contrast of the chest and right arm ordered by surgical oncology did not reveal metastatic disease.

After discussion of the risks, alternatives, and benefits of surgery, the patient elected to try nonsurgical treatment. He was treated with 5-fluorouracil (5-FU) cream 5% twice daily for 4 weeks. It was applied to the right arm from the elbow to the wrist and occluded under an elastic bandage. The patient stated that the biopsy sites became sore and inflamed during the treatment. After 4 weeks of treatment, all 4 KAs had healed without clinical evidence of tumor. During this time, however, the previously treated 2 sites had developed adjacent firm pink papules (Figure, B); these 2 lesions were then treated with intralesional 5-FU 50 mg/mL once weekly to resolution at 4 and 5 weeks, respectively. The proximal lesion was treated with 7.5 mg on week 1 and 5 mg on weeks 2, 3, and 4. The larger distal lesion was treated with 12.5 mg on week 1 and 5 mg on weeks 2, 3, 4, and 5. The volume injected was determined by ability to blanch and indurate the lesion and was decreased due to the shrinking size of the tumor. After 3 injections, both tumors had substantially decreased in size (Figure, C). The patient noted pain during injection but found the procedure tolerable and preferable to surgery. There were no other adverse events. At the end of treatment, both tumors had clinically resolved. No recurrence or development of new tumors was reported over 3 years of follow-up after the last injection.

The development of an expanding neoplastic field appears to play an important role in cutaneous carcinogenesis. It is necessary to consider the cutaneous field cancerization as a highly photodamaged area that contains clinical and subclinical lesions.^2-4 The treatment of cutaneous neoplasms, SCC in particular, should focus not only on the tumor itself but also on the surrounding tissue. Adjunctive field-directed therapies should be considered after treatment of the primary tumor.⁴

Our patient continued to develop SCCs on the right forearm after multiple excisions with clear margins and subsequently was treated with radiation therapy. He then developed 4 KAs after radiation therapy to the right forearm. Topical 5-FU is a well-described treatment of field cancerization.² In our patient, 5-FU cream 5% applied twice daily from the wrist to the elbow under occlusion for 4 weeks led to the involution of all 4 KAs. During this time, our patient developed 2 additional firm pink papules near the previously treated sites, which resolved with intralesional 5-FU weekly for 4 and 5 weeks, respectively.

Intralesional 5-FU has been described for the treatment of multiple and difficult-to-treat KAs. It is an antimetabolite and structural analog of uracil that disrupts DNA and RNA synthesis. It is contraindicated in liver disease, pregnancy or breastfeeding, and allergy to the medication.⁶ Intralesional 5-FU dosing recommendations for KAs include use of a 50-mg/mL solution and injecting 0.1 to 1 mL until the lesion blanches in color, which may be repeated every 1 to 4 weeks.^7,8 The maximum recommended daily dose is 800 mg.⁶ Pretreatment with intralesional 1% lidocaine has been recommended by some authors due to pain with injection.⁸ Recommendations for laboratory monitoring include a complete blood cell count with differential at baseline and weekly. Side effects include local pain, erythema, crusting, ulceration, and necrosis. Systemic side effects include cytopenia and gastrointestinal tract upset.⁶ Intralesional 5-FU has been used successfully in a single dose of 10 mg per lesion in combination with systemic acitretin for the treatment of multiple KAs induced by vemurafenib.⁹ It also has been effective in the treatment of multiple recurrent reactive KAs developing in surgical margins.⁷ A review article reported that the use of intralesional 5-FU produced a 98% cure rate in 56 treated KAs.⁶ Alternative intralesional agents that may be considered for KAs include methotrexate, bleomycin, and interferon alfa-2b.^6,7

Field cancerization may cause the development of multiple clonally related neoplasms within a field of genetically altered cells that may continue to develop after excision with clear margins or radiation therapy. Given the success of treatment in our patient, we recommend consideration for topical and intralesional 5-FU in patients who develop SCCs and KAs within an area of field cancerization.

To the Editor:

The concept of field cancerization has been well described since its initial proposal by Slaughter et al¹ in 1953. It describes a field of genetically altered cells where multiple clonally related neoplasms can develop.^2,3 Treatment of patients with multiple neoplasms within an area of field cancerization can be especially challenging. We report a patient with field cancerization who had multiple squamous cell carcinomas (SCCs) and keratoacanthomas (KAs) that arose within the field.

A 78-year-old man initially presented with a papule on the right forearm of 3 months’ duration. He had a medical history of cutaneous SCC, myocardial infarction, type 2 diabetes mellitus, chronic obstructive pulmonary disease, hypertension, hypercholesterolemia, gout, and diverticulosis. He was not taking any chronic immunosuppressants that may have predisposed him to the development of nonmelanoma skin cancer. The papule was biopsied and diagnosed as a well-differentiated invasive SCC. A month later it was excised with clear margins.

Approximately 5 weeks after the excision, he returned with an enlarging lesion on the right forearm just medial to the excision site. The lesion was biopsied and diagnosed as a well-differentiated SCC. Two months later the lesion was excised with clear margins. Four weeks later he returned with a new lesion adjacent to the medial aspect of the prior excision. The lesion was biopsied and diagnosed as a well-differentiated SCC. Four weeks later the lesion was excised with clear margins.

Another 4 weeks later the patient returned with a new lesion on the excision site. The lesion was biopsied and diagnosed as a well-differentiated SCC. The lesion was treated with radiotherapy, with a 5800-cGy course completed 2 months later. The next month, 2 papules just adjacent to the radiotherapy treatment field were biopsied and diagnosed as well-differentiated SCC, KA type. One week later, 2 additional new papules adjacent to the radiotherapy treatment field were biopsied and diagnosed as moderately differentiated SCC, KA type. At this time, the patient had 4 biopsy-proven KAs on the right forearm in the area of prior radiation (Figure, A). The radiation oncologist felt that further radiation was no longer indicated. A consultation was sought with surgical oncology, and wide excision of the field with sentinel lymph node biopsy and skin grafting was recommended. Computed tomography with contrast of the chest and right arm ordered by surgical oncology did not reveal metastatic disease.

After discussion of the risks, alternatives, and benefits of surgery, the patient elected to try nonsurgical treatment. He was treated with 5-fluorouracil (5-FU) cream 5% twice daily for 4 weeks. It was applied to the right arm from the elbow to the wrist and occluded under an elastic bandage. The patient stated that the biopsy sites became sore and inflamed during the treatment. After 4 weeks of treatment, all 4 KAs had healed without clinical evidence of tumor. During this time, however, the previously treated 2 sites had developed adjacent firm pink papules (Figure, B); these 2 lesions were then treated with intralesional 5-FU 50 mg/mL once weekly to resolution at 4 and 5 weeks, respectively. The proximal lesion was treated with 7.5 mg on week 1 and 5 mg on weeks 2, 3, and 4. The larger distal lesion was treated with 12.5 mg on week 1 and 5 mg on weeks 2, 3, 4, and 5. The volume injected was determined by ability to blanch and indurate the lesion and was decreased due to the shrinking size of the tumor. After 3 injections, both tumors had substantially decreased in size (Figure, C). The patient noted pain during injection but found the procedure tolerable and preferable to surgery. There were no other adverse events. At the end of treatment, both tumors had clinically resolved. No recurrence or development of new tumors was reported over 3 years of follow-up after the last injection.

The development of an expanding neoplastic field appears to play an important role in cutaneous carcinogenesis. It is necessary to consider the cutaneous field cancerization as a highly photodamaged area that contains clinical and subclinical lesions.^2-4 The treatment of cutaneous neoplasms, SCC in particular, should focus not only on the tumor itself but also on the surrounding tissue. Adjunctive field-directed therapies should be considered after treatment of the primary tumor.⁴

Our patient continued to develop SCCs on the right forearm after multiple excisions with clear margins and subsequently was treated with radiation therapy. He then developed 4 KAs after radiation therapy to the right forearm. Topical 5-FU is a well-described treatment of field cancerization.² In our patient, 5-FU cream 5% applied twice daily from the wrist to the elbow under occlusion for 4 weeks led to the involution of all 4 KAs. During this time, our patient developed 2 additional firm pink papules near the previously treated sites, which resolved with intralesional 5-FU weekly for 4 and 5 weeks, respectively.

Intralesional 5-FU has been described for the treatment of multiple and difficult-to-treat KAs. It is an antimetabolite and structural analog of uracil that disrupts DNA and RNA synthesis. It is contraindicated in liver disease, pregnancy or breastfeeding, and allergy to the medication.⁶ Intralesional 5-FU dosing recommendations for KAs include use of a 50-mg/mL solution and injecting 0.1 to 1 mL until the lesion blanches in color, which may be repeated every 1 to 4 weeks.^7,8 The maximum recommended daily dose is 800 mg.⁶ Pretreatment with intralesional 1% lidocaine has been recommended by some authors due to pain with injection.⁸ Recommendations for laboratory monitoring include a complete blood cell count with differential at baseline and weekly. Side effects include local pain, erythema, crusting, ulceration, and necrosis. Systemic side effects include cytopenia and gastrointestinal tract upset.⁶ Intralesional 5-FU has been used successfully in a single dose of 10 mg per lesion in combination with systemic acitretin for the treatment of multiple KAs induced by vemurafenib.⁹ It also has been effective in the treatment of multiple recurrent reactive KAs developing in surgical margins.⁷ A review article reported that the use of intralesional 5-FU produced a 98% cure rate in 56 treated KAs.⁶ Alternative intralesional agents that may be considered for KAs include methotrexate, bleomycin, and interferon alfa-2b.^6,7

Field cancerization may cause the development of multiple clonally related neoplasms within a field of genetically altered cells that may continue to develop after excision with clear margins or radiation therapy. Given the success of treatment in our patient, we recommend consideration for topical and intralesional 5-FU in patients who develop SCCs and KAs within an area of field cancerization.

To the Editor:

The concept of field cancerization has been well described since its initial proposal by Slaughter et al¹ in 1953. It describes a field of genetically altered cells where multiple clonally related neoplasms can develop.^2,3 Treatment of patients with multiple neoplasms within an area of field cancerization can be especially challenging. We report a patient with field cancerization who had multiple squamous cell carcinomas (SCCs) and keratoacanthomas (KAs) that arose within the field.

A 78-year-old man initially presented with a papule on the right forearm of 3 months’ duration. He had a medical history of cutaneous SCC, myocardial infarction, type 2 diabetes mellitus, chronic obstructive pulmonary disease, hypertension, hypercholesterolemia, gout, and diverticulosis. He was not taking any chronic immunosuppressants that may have predisposed him to the development of nonmelanoma skin cancer. The papule was biopsied and diagnosed as a well-differentiated invasive SCC. A month later it was excised with clear margins.

Approximately 5 weeks after the excision, he returned with an enlarging lesion on the right forearm just medial to the excision site. The lesion was biopsied and diagnosed as a well-differentiated SCC. Two months later the lesion was excised with clear margins. Four weeks later he returned with a new lesion adjacent to the medial aspect of the prior excision. The lesion was biopsied and diagnosed as a well-differentiated SCC. Four weeks later the lesion was excised with clear margins.

Another 4 weeks later the patient returned with a new lesion on the excision site. The lesion was biopsied and diagnosed as a well-differentiated SCC. The lesion was treated with radiotherapy, with a 5800-cGy course completed 2 months later. The next month, 2 papules just adjacent to the radiotherapy treatment field were biopsied and diagnosed as well-differentiated SCC, KA type. One week later, 2 additional new papules adjacent to the radiotherapy treatment field were biopsied and diagnosed as moderately differentiated SCC, KA type. At this time, the patient had 4 biopsy-proven KAs on the right forearm in the area of prior radiation (Figure, A). The radiation oncologist felt that further radiation was no longer indicated. A consultation was sought with surgical oncology, and wide excision of the field with sentinel lymph node biopsy and skin grafting was recommended. Computed tomography with contrast of the chest and right arm ordered by surgical oncology did not reveal metastatic disease.

After discussion of the risks, alternatives, and benefits of surgery, the patient elected to try nonsurgical treatment. He was treated with 5-fluorouracil (5-FU) cream 5% twice daily for 4 weeks. It was applied to the right arm from the elbow to the wrist and occluded under an elastic bandage. The patient stated that the biopsy sites became sore and inflamed during the treatment. After 4 weeks of treatment, all 4 KAs had healed without clinical evidence of tumor. During this time, however, the previously treated 2 sites had developed adjacent firm pink papules (Figure, B); these 2 lesions were then treated with intralesional 5-FU 50 mg/mL once weekly to resolution at 4 and 5 weeks, respectively. The proximal lesion was treated with 7.5 mg on week 1 and 5 mg on weeks 2, 3, and 4. The larger distal lesion was treated with 12.5 mg on week 1 and 5 mg on weeks 2, 3, 4, and 5. The volume injected was determined by ability to blanch and indurate the lesion and was decreased due to the shrinking size of the tumor. After 3 injections, both tumors had substantially decreased in size (Figure, C). The patient noted pain during injection but found the procedure tolerable and preferable to surgery. There were no other adverse events. At the end of treatment, both tumors had clinically resolved. No recurrence or development of new tumors was reported over 3 years of follow-up after the last injection.

The development of an expanding neoplastic field appears to play an important role in cutaneous carcinogenesis. It is necessary to consider the cutaneous field cancerization as a highly photodamaged area that contains clinical and subclinical lesions.^2-4 The treatment of cutaneous neoplasms, SCC in particular, should focus not only on the tumor itself but also on the surrounding tissue. Adjunctive field-directed therapies should be considered after treatment of the primary tumor.⁴

Our patient continued to develop SCCs on the right forearm after multiple excisions with clear margins and subsequently was treated with radiation therapy. He then developed 4 KAs after radiation therapy to the right forearm. Topical 5-FU is a well-described treatment of field cancerization.² In our patient, 5-FU cream 5% applied twice daily from the wrist to the elbow under occlusion for 4 weeks led to the involution of all 4 KAs. During this time, our patient developed 2 additional firm pink papules near the previously treated sites, which resolved with intralesional 5-FU weekly for 4 and 5 weeks, respectively.

Intralesional 5-FU has been described for the treatment of multiple and difficult-to-treat KAs. It is an antimetabolite and structural analog of uracil that disrupts DNA and RNA synthesis. It is contraindicated in liver disease, pregnancy or breastfeeding, and allergy to the medication.⁶ Intralesional 5-FU dosing recommendations for KAs include use of a 50-mg/mL solution and injecting 0.1 to 1 mL until the lesion blanches in color, which may be repeated every 1 to 4 weeks.^7,8 The maximum recommended daily dose is 800 mg.⁶ Pretreatment with intralesional 1% lidocaine has been recommended by some authors due to pain with injection.⁸ Recommendations for laboratory monitoring include a complete blood cell count with differential at baseline and weekly. Side effects include local pain, erythema, crusting, ulceration, and necrosis. Systemic side effects include cytopenia and gastrointestinal tract upset.⁶ Intralesional 5-FU has been used successfully in a single dose of 10 mg per lesion in combination with systemic acitretin for the treatment of multiple KAs induced by vemurafenib.⁹ It also has been effective in the treatment of multiple recurrent reactive KAs developing in surgical margins.⁷ A review article reported that the use of intralesional 5-FU produced a 98% cure rate in 56 treated KAs.⁶ Alternative intralesional agents that may be considered for KAs include methotrexate, bleomycin, and interferon alfa-2b.^6,7

Field cancerization may cause the development of multiple clonally related neoplasms within a field of genetically altered cells that may continue to develop after excision with clear margins or radiation therapy. Given the success of treatment in our patient, we recommend consideration for topical and intralesional 5-FU in patients who develop SCCs and KAs within an area of field cancerization.

Merkel cell carcinoma (MCC) is a rare, rapidly growing, aggressive neoplasm with a generally poor prognosis. The cells of origin are highly anaplastic and share structural and immunohistochemical features with various neuroectodermally derived cells. Although Merkel cells, which are slow-acting cutaneous mechanoreceptors located in the basal layer of the epidermis, and MCC share immunohistochemical and ultrastructural features, there is limited evidence of a direct histogenetic relationship between the two.^1,2 Additionally, some extracutaneous neuroendocrine tumors have features similar to MCC; therefore, although it may be more accurate and perhaps more practical to describe these lesions as primary neuroendocrine carcinomas of the skin, the term MCC is more commonly used both in the literature and in clinical practice.^1,2

Merkel cell carcinoma typically presents in the head and neck region in white patients older than 70 years of age and in the immunocompromised population.^3-6 The mean age of diagnosis is 76 years for women and 74 years for men.⁷ The incidence of MCC in the United States tripled over a 15-year period, and there are approximately 1500 new cases of MCC diagnosed each year, making it about 40 times less common than melanoma.⁸ The 5-year survival rate for patients without lymph node involvement is 75%, whereas the 5-year survival rate for patients with distant metastases is 25%.⁹

Merkel cell carcinoma is thought to develop through 1 of 2 distinct pathways. In a virally mediated pathway, which represents at least 80% of cases, the Merkel cell polyomavirus (MCV) monoclonally integrates into the host genome and promotes oncogenesis via altered p53 and retinoblastoma protein expression.^10-12 The remainder of cases are believed to develop via a nonvirally mediated pathway in which genetic anomalies, immune status, and environmental factors influence oncogenesis.^10-13

Due to the similarity between MCC and metastatic neuroendocrine neoplasms, especially small-cell lung carcinomas, immunohistochemistry is important in making the diagnosis. Cytokeratin 20 and neuron-specific enolase positivity and thyroid transcription factor 1 negativity are the most useful markers in identifying MCC.

Regression of MCC is a very rare and poorly understood event. A 2010 review of the literature described 22 cases of spontaneous regression.¹⁴ We report a rare case of rapid and complete regression of MCC following punch biopsy in a 96-year-old woman.

Case Report

A 96-year-old woman presented with a rapidly enlarging lesion overlying the suprasternal notch of 8 weeks’ duration (Figure 1). The lesion consisted of a 5.0×4.5-cm, friable, erythematous, flesh-colored nodule with ulceration and heavy crusting. Surrounding the nodule was an erythematous to violaceous patch extending to the anterior chest and bilateral supraclavicular area. No cervical or clavicular lymphadenopathy was observed. According to the patient’s caregiver, the lesion originated as a small, erythematous, scaly macule that rapidly increased in size over an 8-week period to a maximum of 5.0×4.5 cm at presentation. The lesion bled on 2 or 3 occasions during the 8-week period and was controlled with a warm compress. The patient’s caregiver had treated the lesion with topical tea tree oil (for malodor) and antibiotic ointment as needed. The clinical differential diagnosis included squamous cell carcinoma, keratoacanthoma, amelanotic melanoma, cutaneous metastasis of a primary visceral malignancy, basal cell carcinoma, and MCC. Biopsy of the lesion was recommended at this time but the patient’s family declined.

A 4-mm punch biopsy was obtained at a follow-up visit 4 weeks later (12 weeks after the reported onset of the lesion). Hematoxylin and eosin staining showed a small-cell neoplasm with stippled nuclei and scant cytoplasm forming a nested and somewhat trabecular pattern. Mitotic activity, apoptosis, and nuclear molding also were present (Figure 2). The tumor cells were positive for cytokeratin 20 with a dotlike, paranuclear pattern (Figure 3). Staining for CAM 5.2 also was positive. Cytokeratin 5/6, human melanoma black 45, and leukocyte common antigen were negative. The immunophenotyping of the lymphocytic response to the tumor showed that the majority of intratumoral lymphocytes were CD8 positive (Figure 4). CD4-positive lymphocytes were predominantly seen at the periphery of the tumor nests without tumor infiltration (Figure 5). Based on these findings, a diagnosis of MCC was made. The patient’s family declined treatment based on her advanced age and current health status, which included advanced dementia.

Two weeks after the punch biopsy, the lesion had noticeably decreased in size and lost its dome-shaped appearance. Within 8 weeks after biopsy (20 weeks since the lesion first appeared), the lesion had completely resolved (Figure 6). The patient was lost to follow-up months later, but no recurrence of the lesion was reported.

Comment

Spontaneous regression is not unique to MCC, as this phenomenon also has been reported in keratoacanthoma, lymphoma, basal cell carcinoma, and melanoma.¹⁵ Complete spontaneous regression is defined as occurring in the absence of therapy that is intended to have a treatment effect.^15,16 Spontaneous regression is estimated to occur in malignant neoplasms at a rate of 1 case per 60,000 to 100,000 (approximately 0.0013% of all malignant neoplasms).¹⁷ Considering the reported prevalence of MCC and the number of cases that have been known to regress, the estimated incidence of complete spontaneous regression may be as high as 1.5%.¹⁴ Though spontaneous regression of MCC is more prevalent than expected, it still is considered a rare phenomenon. A 2010 review of the literature yielded 22 cases of complete spontaneous regression of MCC.¹⁴ No recurrences have been observed; however, follow-up was relatively short in some cases.

In a unique report by Bertolotti et al,¹⁸ a patient with MCC on the nasal tip presented 4 weeks after biopsy with complete spontaneous regression of the tumor, which was associated with bilateral cervical lymph node involvement as noted by hypermetabolic uptake on positron emission tomography scanning. The patient underwent radiation therapy and was disease free at 12 months’ follow-up.¹⁸

Complete spontaneous regression has been described in MCC patients with local disease, regional recurrences, and metastatic disease.¹⁹ In all reviewed cases, the regression is a fairly quick phenomenon occurring over the course of 1 to 5 months.^16,19,20,21 Our patient presented with advanced age and a tumor location characteristic of MCC. In our search of PubMed articles indexed for MEDLINE using the terms MCC, Merkel cell carcinoma, regression, and spontaneous regression, all but 1 case of MCC regression involved tumors that were located on the head.¹⁴

The histopathologic features observed in our case, specifically intratumoral CD8-positive cytotoxic lymphocytes and peritumoral CD4-positive cells, were similar to the findings in other reported cases. In one series of 2 cases, the one case showed scar tissue with a moderate, predominantly T-lymphocytic infiltrate and no tumor cells, and the second showed cellular proliferation in the deep dermis with dense lymphocytic infiltrates primarily composed of CD3-positive T cells.¹⁴ Other studies of regression of both localized and metastatic MCC demonstrated infiltration by CD4-positive, CD8-positive, and CD3-positive lymphocytes and foamy macrophages.^21-23

The discovery of the MCV was one of the most important advances in elucidating the pathogenesis of MCC.^10,24-26 Merkel cell polyomavirus DNA has been detected in a majority of MCC cases.^25,27 Viral integration has been shown to take place early, prior to tumor clonal expansion.¹⁰ Importantly, not all cases of MCC show MCV infection, and MCV infection is not exclusive to MCC.²⁸ Merkel cell polyomavirus is considered to be part of the normal human flora, and asymptomatic infection is quite common.²⁹ It has been identified in 80% of adults older than 50 years of age and, interestingly, in 35% of children by 13 years of age or younger.^30,31 It remains unclear what role the presence of MCV plays in determining MCC prognosis. Several reports have demonstrated lower disease-specific mortality associated with MCV-positive MCC.^32-35 In contrast, Schrama et al³⁶ correlated the MCV status of 174 MCC tumors and found no difference in clinical behavior or prognosis between MCV-positive and MCV-negative MCCs.

Immunosuppression also may play a role in the development of MCC.^5,25 There is increased prevalence of MCC in the human immunodeficiency virus–positive population, as well as in organ-transplant recipients and patients with leukemia. Chronic lymphocytic leukemia seems to be the most frequent neoplasia associated with development of MCC.³⁷

The mechanism of MCC regression remains unclear, but many investigators emphasize the importance of T-cell–mediated immunity.^{16,21-23,38,39} Apoptosis also has been shown to play an important role.⁴⁰ Our case showed tumor-infiltrating CD8-positive lymphocytes and CD4-positive lymphocytes present predominantly at the periphery of the tumor, with close proximity to the tumor nests but with no tumor infiltration (Figure 3). This distribution was consistently present in multiple sections of the tumor. These findings are consistent with prior reports of both CD4-positive and CD8-positive T lymphocytes associated with MCC regression. Our findings confirm that immune response may play an important role in spontaneous regression of MCC.

There is much speculation regarding the initial biopsy of an MCC lesion (or other traumatic event) and its role in tumor regression. Koba et al⁴¹ examined the effect of biopsy on CD8-positive lymphocytic infiltration of MCC tumor cells and found that biopsy does not commonly alter intratumoral CD8-positive infiltration. These findings suggest trauma does not directly induce immunologic recognition of this cancer.

Conclusion

We report a case of complete spontaneous regression of a localized MCC following a punch biopsy. The histopathology showed a brisk T-lymphocyte response with intratumoral CD8-positive cytotoxic lymphocytes and peritumoral CD4-positive cells. The age and clinical profile of our patient as well as the clinicopathologic characteristics of the tumor regression are similar to other reported cases. Further research is needed to elucidate the mechanism of MCC regression, and a better understanding of this fascinating phenomenon could help in development of new immunotherapeutic approaches.

Merkel cell carcinoma (MCC) is a rare, rapidly growing, aggressive neoplasm with a generally poor prognosis. The cells of origin are highly anaplastic and share structural and immunohistochemical features with various neuroectodermally derived cells. Although Merkel cells, which are slow-acting cutaneous mechanoreceptors located in the basal layer of the epidermis, and MCC share immunohistochemical and ultrastructural features, there is limited evidence of a direct histogenetic relationship between the two.^1,2 Additionally, some extracutaneous neuroendocrine tumors have features similar to MCC; therefore, although it may be more accurate and perhaps more practical to describe these lesions as primary neuroendocrine carcinomas of the skin, the term MCC is more commonly used both in the literature and in clinical practice.^1,2

Merkel cell carcinoma typically presents in the head and neck region in white patients older than 70 years of age and in the immunocompromised population.^3-6 The mean age of diagnosis is 76 years for women and 74 years for men.⁷ The incidence of MCC in the United States tripled over a 15-year period, and there are approximately 1500 new cases of MCC diagnosed each year, making it about 40 times less common than melanoma.⁸ The 5-year survival rate for patients without lymph node involvement is 75%, whereas the 5-year survival rate for patients with distant metastases is 25%.⁹

Merkel cell carcinoma is thought to develop through 1 of 2 distinct pathways. In a virally mediated pathway, which represents at least 80% of cases, the Merkel cell polyomavirus (MCV) monoclonally integrates into the host genome and promotes oncogenesis via altered p53 and retinoblastoma protein expression.^10-12 The remainder of cases are believed to develop via a nonvirally mediated pathway in which genetic anomalies, immune status, and environmental factors influence oncogenesis.^10-13

Due to the similarity between MCC and metastatic neuroendocrine neoplasms, especially small-cell lung carcinomas, immunohistochemistry is important in making the diagnosis. Cytokeratin 20 and neuron-specific enolase positivity and thyroid transcription factor 1 negativity are the most useful markers in identifying MCC.

Regression of MCC is a very rare and poorly understood event. A 2010 review of the literature described 22 cases of spontaneous regression.¹⁴ We report a rare case of rapid and complete regression of MCC following punch biopsy in a 96-year-old woman.

Case Report

A 96-year-old woman presented with a rapidly enlarging lesion overlying the suprasternal notch of 8 weeks’ duration (Figure 1). The lesion consisted of a 5.0×4.5-cm, friable, erythematous, flesh-colored nodule with ulceration and heavy crusting. Surrounding the nodule was an erythematous to violaceous patch extending to the anterior chest and bilateral supraclavicular area. No cervical or clavicular lymphadenopathy was observed. According to the patient’s caregiver, the lesion originated as a small, erythematous, scaly macule that rapidly increased in size over an 8-week period to a maximum of 5.0×4.5 cm at presentation. The lesion bled on 2 or 3 occasions during the 8-week period and was controlled with a warm compress. The patient’s caregiver had treated the lesion with topical tea tree oil (for malodor) and antibiotic ointment as needed. The clinical differential diagnosis included squamous cell carcinoma, keratoacanthoma, amelanotic melanoma, cutaneous metastasis of a primary visceral malignancy, basal cell carcinoma, and MCC. Biopsy of the lesion was recommended at this time but the patient’s family declined.

A 4-mm punch biopsy was obtained at a follow-up visit 4 weeks later (12 weeks after the reported onset of the lesion). Hematoxylin and eosin staining showed a small-cell neoplasm with stippled nuclei and scant cytoplasm forming a nested and somewhat trabecular pattern. Mitotic activity, apoptosis, and nuclear molding also were present (Figure 2). The tumor cells were positive for cytokeratin 20 with a dotlike, paranuclear pattern (Figure 3). Staining for CAM 5.2 also was positive. Cytokeratin 5/6, human melanoma black 45, and leukocyte common antigen were negative. The immunophenotyping of the lymphocytic response to the tumor showed that the majority of intratumoral lymphocytes were CD8 positive (Figure 4). CD4-positive lymphocytes were predominantly seen at the periphery of the tumor nests without tumor infiltration (Figure 5). Based on these findings, a diagnosis of MCC was made. The patient’s family declined treatment based on her advanced age and current health status, which included advanced dementia.

Two weeks after the punch biopsy, the lesion had noticeably decreased in size and lost its dome-shaped appearance. Within 8 weeks after biopsy (20 weeks since the lesion first appeared), the lesion had completely resolved (Figure 6). The patient was lost to follow-up months later, but no recurrence of the lesion was reported.

Comment

Spontaneous regression is not unique to MCC, as this phenomenon also has been reported in keratoacanthoma, lymphoma, basal cell carcinoma, and melanoma.¹⁵ Complete spontaneous regression is defined as occurring in the absence of therapy that is intended to have a treatment effect.^15,16 Spontaneous regression is estimated to occur in malignant neoplasms at a rate of 1 case per 60,000 to 100,000 (approximately 0.0013% of all malignant neoplasms).¹⁷ Considering the reported prevalence of MCC and the number of cases that have been known to regress, the estimated incidence of complete spontaneous regression may be as high as 1.5%.¹⁴ Though spontaneous regression of MCC is more prevalent than expected, it still is considered a rare phenomenon. A 2010 review of the literature yielded 22 cases of complete spontaneous regression of MCC.¹⁴ No recurrences have been observed; however, follow-up was relatively short in some cases.

In a unique report by Bertolotti et al,¹⁸ a patient with MCC on the nasal tip presented 4 weeks after biopsy with complete spontaneous regression of the tumor, which was associated with bilateral cervical lymph node involvement as noted by hypermetabolic uptake on positron emission tomography scanning. The patient underwent radiation therapy and was disease free at 12 months’ follow-up.¹⁸

Complete spontaneous regression has been described in MCC patients with local disease, regional recurrences, and metastatic disease.¹⁹ In all reviewed cases, the regression is a fairly quick phenomenon occurring over the course of 1 to 5 months.^16,19,20,21 Our patient presented with advanced age and a tumor location characteristic of MCC. In our search of PubMed articles indexed for MEDLINE using the terms MCC, Merkel cell carcinoma, regression, and spontaneous regression, all but 1 case of MCC regression involved tumors that were located on the head.¹⁴

The histopathologic features observed in our case, specifically intratumoral CD8-positive cytotoxic lymphocytes and peritumoral CD4-positive cells, were similar to the findings in other reported cases. In one series of 2 cases, the one case showed scar tissue with a moderate, predominantly T-lymphocytic infiltrate and no tumor cells, and the second showed cellular proliferation in the deep dermis with dense lymphocytic infiltrates primarily composed of CD3-positive T cells.¹⁴ Other studies of regression of both localized and metastatic MCC demonstrated infiltration by CD4-positive, CD8-positive, and CD3-positive lymphocytes and foamy macrophages.^21-23

The discovery of the MCV was one of the most important advances in elucidating the pathogenesis of MCC.^10,24-26 Merkel cell polyomavirus DNA has been detected in a majority of MCC cases.^25,27 Viral integration has been shown to take place early, prior to tumor clonal expansion.¹⁰ Importantly, not all cases of MCC show MCV infection, and MCV infection is not exclusive to MCC.²⁸ Merkel cell polyomavirus is considered to be part of the normal human flora, and asymptomatic infection is quite common.²⁹ It has been identified in 80% of adults older than 50 years of age and, interestingly, in 35% of children by 13 years of age or younger.^30,31 It remains unclear what role the presence of MCV plays in determining MCC prognosis. Several reports have demonstrated lower disease-specific mortality associated with MCV-positive MCC.^32-35 In contrast, Schrama et al³⁶ correlated the MCV status of 174 MCC tumors and found no difference in clinical behavior or prognosis between MCV-positive and MCV-negative MCCs.

Immunosuppression also may play a role in the development of MCC.^5,25 There is increased prevalence of MCC in the human immunodeficiency virus–positive population, as well as in organ-transplant recipients and patients with leukemia. Chronic lymphocytic leukemia seems to be the most frequent neoplasia associated with development of MCC.³⁷

The mechanism of MCC regression remains unclear, but many investigators emphasize the importance of T-cell–mediated immunity.^{16,21-23,38,39} Apoptosis also has been shown to play an important role.⁴⁰ Our case showed tumor-infiltrating CD8-positive lymphocytes and CD4-positive lymphocytes present predominantly at the periphery of the tumor, with close proximity to the tumor nests but with no tumor infiltration (Figure 3). This distribution was consistently present in multiple sections of the tumor. These findings are consistent with prior reports of both CD4-positive and CD8-positive T lymphocytes associated with MCC regression. Our findings confirm that immune response may play an important role in spontaneous regression of MCC.

There is much speculation regarding the initial biopsy of an MCC lesion (or other traumatic event) and its role in tumor regression. Koba et al⁴¹ examined the effect of biopsy on CD8-positive lymphocytic infiltration of MCC tumor cells and found that biopsy does not commonly alter intratumoral CD8-positive infiltration. These findings suggest trauma does not directly induce immunologic recognition of this cancer.

Conclusion

We report a case of complete spontaneous regression of a localized MCC following a punch biopsy. The histopathology showed a brisk T-lymphocyte response with intratumoral CD8-positive cytotoxic lymphocytes and peritumoral CD4-positive cells. The age and clinical profile of our patient as well as the clinicopathologic characteristics of the tumor regression are similar to other reported cases. Further research is needed to elucidate the mechanism of MCC regression, and a better understanding of this fascinating phenomenon could help in development of new immunotherapeutic approaches.

Merkel cell carcinoma (MCC) is a rare, rapidly growing, aggressive neoplasm with a generally poor prognosis. The cells of origin are highly anaplastic and share structural and immunohistochemical features with various neuroectodermally derived cells. Although Merkel cells, which are slow-acting cutaneous mechanoreceptors located in the basal layer of the epidermis, and MCC share immunohistochemical and ultrastructural features, there is limited evidence of a direct histogenetic relationship between the two.^1,2 Additionally, some extracutaneous neuroendocrine tumors have features similar to MCC; therefore, although it may be more accurate and perhaps more practical to describe these lesions as primary neuroendocrine carcinomas of the skin, the term MCC is more commonly used both in the literature and in clinical practice.^1,2

Merkel cell carcinoma typically presents in the head and neck region in white patients older than 70 years of age and in the immunocompromised population.^3-6 The mean age of diagnosis is 76 years for women and 74 years for men.⁷ The incidence of MCC in the United States tripled over a 15-year period, and there are approximately 1500 new cases of MCC diagnosed each year, making it about 40 times less common than melanoma.⁸ The 5-year survival rate for patients without lymph node involvement is 75%, whereas the 5-year survival rate for patients with distant metastases is 25%.⁹

Merkel cell carcinoma is thought to develop through 1 of 2 distinct pathways. In a virally mediated pathway, which represents at least 80% of cases, the Merkel cell polyomavirus (MCV) monoclonally integrates into the host genome and promotes oncogenesis via altered p53 and retinoblastoma protein expression.^10-12 The remainder of cases are believed to develop via a nonvirally mediated pathway in which genetic anomalies, immune status, and environmental factors influence oncogenesis.^10-13

Due to the similarity between MCC and metastatic neuroendocrine neoplasms, especially small-cell lung carcinomas, immunohistochemistry is important in making the diagnosis. Cytokeratin 20 and neuron-specific enolase positivity and thyroid transcription factor 1 negativity are the most useful markers in identifying MCC.

Regression of MCC is a very rare and poorly understood event. A 2010 review of the literature described 22 cases of spontaneous regression.¹⁴ We report a rare case of rapid and complete regression of MCC following punch biopsy in a 96-year-old woman.

Case Report

A 96-year-old woman presented with a rapidly enlarging lesion overlying the suprasternal notch of 8 weeks’ duration (Figure 1). The lesion consisted of a 5.0×4.5-cm, friable, erythematous, flesh-colored nodule with ulceration and heavy crusting. Surrounding the nodule was an erythematous to violaceous patch extending to the anterior chest and bilateral supraclavicular area. No cervical or clavicular lymphadenopathy was observed. According to the patient’s caregiver, the lesion originated as a small, erythematous, scaly macule that rapidly increased in size over an 8-week period to a maximum of 5.0×4.5 cm at presentation. The lesion bled on 2 or 3 occasions during the 8-week period and was controlled with a warm compress. The patient’s caregiver had treated the lesion with topical tea tree oil (for malodor) and antibiotic ointment as needed. The clinical differential diagnosis included squamous cell carcinoma, keratoacanthoma, amelanotic melanoma, cutaneous metastasis of a primary visceral malignancy, basal cell carcinoma, and MCC. Biopsy of the lesion was recommended at this time but the patient’s family declined.

A 4-mm punch biopsy was obtained at a follow-up visit 4 weeks later (12 weeks after the reported onset of the lesion). Hematoxylin and eosin staining showed a small-cell neoplasm with stippled nuclei and scant cytoplasm forming a nested and somewhat trabecular pattern. Mitotic activity, apoptosis, and nuclear molding also were present (Figure 2). The tumor cells were positive for cytokeratin 20 with a dotlike, paranuclear pattern (Figure 3). Staining for CAM 5.2 also was positive. Cytokeratin 5/6, human melanoma black 45, and leukocyte common antigen were negative. The immunophenotyping of the lymphocytic response to the tumor showed that the majority of intratumoral lymphocytes were CD8 positive (Figure 4). CD4-positive lymphocytes were predominantly seen at the periphery of the tumor nests without tumor infiltration (Figure 5). Based on these findings, a diagnosis of MCC was made. The patient’s family declined treatment based on her advanced age and current health status, which included advanced dementia.

Two weeks after the punch biopsy, the lesion had noticeably decreased in size and lost its dome-shaped appearance. Within 8 weeks after biopsy (20 weeks since the lesion first appeared), the lesion had completely resolved (Figure 6). The patient was lost to follow-up months later, but no recurrence of the lesion was reported.

Comment

Spontaneous regression is not unique to MCC, as this phenomenon also has been reported in keratoacanthoma, lymphoma, basal cell carcinoma, and melanoma.¹⁵ Complete spontaneous regression is defined as occurring in the absence of therapy that is intended to have a treatment effect.^15,16 Spontaneous regression is estimated to occur in malignant neoplasms at a rate of 1 case per 60,000 to 100,000 (approximately 0.0013% of all malignant neoplasms).¹⁷ Considering the reported prevalence of MCC and the number of cases that have been known to regress, the estimated incidence of complete spontaneous regression may be as high as 1.5%.¹⁴ Though spontaneous regression of MCC is more prevalent than expected, it still is considered a rare phenomenon. A 2010 review of the literature yielded 22 cases of complete spontaneous regression of MCC.¹⁴ No recurrences have been observed; however, follow-up was relatively short in some cases.

In a unique report by Bertolotti et al,¹⁸ a patient with MCC on the nasal tip presented 4 weeks after biopsy with complete spontaneous regression of the tumor, which was associated with bilateral cervical lymph node involvement as noted by hypermetabolic uptake on positron emission tomography scanning. The patient underwent radiation therapy and was disease free at 12 months’ follow-up.¹⁸

Complete spontaneous regression has been described in MCC patients with local disease, regional recurrences, and metastatic disease.¹⁹ In all reviewed cases, the regression is a fairly quick phenomenon occurring over the course of 1 to 5 months.^16,19,20,21 Our patient presented with advanced age and a tumor location characteristic of MCC. In our search of PubMed articles indexed for MEDLINE using the terms MCC, Merkel cell carcinoma, regression, and spontaneous regression, all but 1 case of MCC regression involved tumors that were located on the head.¹⁴

The histopathologic features observed in our case, specifically intratumoral CD8-positive cytotoxic lymphocytes and peritumoral CD4-positive cells, were similar to the findings in other reported cases. In one series of 2 cases, the one case showed scar tissue with a moderate, predominantly T-lymphocytic infiltrate and no tumor cells, and the second showed cellular proliferation in the deep dermis with dense lymphocytic infiltrates primarily composed of CD3-positive T cells.¹⁴ Other studies of regression of both localized and metastatic MCC demonstrated infiltration by CD4-positive, CD8-positive, and CD3-positive lymphocytes and foamy macrophages.^21-23

The discovery of the MCV was one of the most important advances in elucidating the pathogenesis of MCC.^10,24-26 Merkel cell polyomavirus DNA has been detected in a majority of MCC cases.^25,27 Viral integration has been shown to take place early, prior to tumor clonal expansion.¹⁰ Importantly, not all cases of MCC show MCV infection, and MCV infection is not exclusive to MCC.²⁸ Merkel cell polyomavirus is considered to be part of the normal human flora, and asymptomatic infection is quite common.²⁹ It has been identified in 80% of adults older than 50 years of age and, interestingly, in 35% of children by 13 years of age or younger.^30,31 It remains unclear what role the presence of MCV plays in determining MCC prognosis. Several reports have demonstrated lower disease-specific mortality associated with MCV-positive MCC.^32-35 In contrast, Schrama et al³⁶ correlated the MCV status of 174 MCC tumors and found no difference in clinical behavior or prognosis between MCV-positive and MCV-negative MCCs.

Immunosuppression also may play a role in the development of MCC.^5,25 There is increased prevalence of MCC in the human immunodeficiency virus–positive population, as well as in organ-transplant recipients and patients with leukemia. Chronic lymphocytic leukemia seems to be the most frequent neoplasia associated with development of MCC.³⁷

The mechanism of MCC regression remains unclear, but many investigators emphasize the importance of T-cell–mediated immunity.^{16,21-23,38,39} Apoptosis also has been shown to play an important role.⁴⁰ Our case showed tumor-infiltrating CD8-positive lymphocytes and CD4-positive lymphocytes present predominantly at the periphery of the tumor, with close proximity to the tumor nests but with no tumor infiltration (Figure 3). This distribution was consistently present in multiple sections of the tumor. These findings are consistent with prior reports of both CD4-positive and CD8-positive T lymphocytes associated with MCC regression. Our findings confirm that immune response may play an important role in spontaneous regression of MCC.

There is much speculation regarding the initial biopsy of an MCC lesion (or other traumatic event) and its role in tumor regression. Koba et al⁴¹ examined the effect of biopsy on CD8-positive lymphocytic infiltration of MCC tumor cells and found that biopsy does not commonly alter intratumoral CD8-positive infiltration. These findings suggest trauma does not directly induce immunologic recognition of this cancer.

Conclusion

We report a case of complete spontaneous regression of a localized MCC following a punch biopsy. The histopathology showed a brisk T-lymphocyte response with intratumoral CD8-positive cytotoxic lymphocytes and peritumoral CD4-positive cells. The age and clinical profile of our patient as well as the clinicopathologic characteristics of the tumor regression are similar to other reported cases. Further research is needed to elucidate the mechanism of MCC regression, and a better understanding of this fascinating phenomenon could help in development of new immunotherapeutic approaches.