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Dermatopathologist Michi M. Shinohara, MD, is often asked why it takes so long to diagnose mycosis fungoides. Her reply: Early histopathologic findings in mycosis fungoides (MF) can be subtle, and accurate diagnosis is aided by taking multiple skin biopsies from different sites sequentially over time when there’s diagnostic uncertainty.
“Take multiple biopsies. There is clear literature that taking multiple biopsies from different areas of the body can really increase the sensitivity and specificity of TCR/PCR [T-cell receptor gene PCR clonality studies],” she said at a virtual forum on cutaneous malignancies jointly presented by the Postgraduate Institute for Medicine and Global Academy for Medical Education.
Patients with MF carry multiple subclones, and by taking multiple skin biopsies, different expression patterns may be revealed.
“MF is incredibly mutationally complex, and that has implications for therapy. There is certainly no single, nor even a few, targetable mutations. There are over 50 driver mutations known in CTCL [cutaneous T-cell lymphoma] involving more than a dozen signaling pathways,” said Dr. Shinohara, codirector of the cutaneous lymphoma clinic at the Seattle Cancer Care Alliance and director of dermatopathology at the University of Washington, Seattle.
MF is a lymphoma of skin-resident memory T-cells, the same T-cells involved in the pathogenesis of fixed drug eruption. MF accounts for about half of primary CTCLs. Traditionally, the average time from appearance of skin lesions to definitive diagnosis of MF is 3-6 years.
The International Society for Cutaneous Lymphomas diagnostic algorithm emphasizes that accurate diagnosis of MF requires clinical and histopathologic correlation supported by immunohistochemistry and TCR/PCR or other molecular studies. In an independent validation study, the algorithm demonstrated a sensitivity of 87.5% and specificity of 60% for diagnosis of MF.
Using this algorithm, a diagnosis of MF requires 4 points or more. A maximum of 2 points is available for the key clinical findings of variably sized persistent patches and/or plaques on non–sun-exposed areas, with poikiloderma. Another maximum of 2 points is awarded for the classic histopathologic findings consistent with MF and other forms of cutaneous T-cell lymphoma – namely, a superficial lymphoid infiltrate with epidermotropic but not spongiotic atypia. A positive immunohistochemical study is worth 1 point, and another point is granted for a positive result from a molecular study; both the immunohistochemical and molecular studies should “almost always” be done in patients with suspected MF, whereas a bone marrow biopsy is almost never appropriate.
The challenge for dermatopathologists in making an early diagnosis of MF is that, in patch-stage disease, many of the patient’s own cytotoxic CD8+ T-cells are present in the biopsy specimen battling the malignancy. These tumor-fighting cells often mask the malignant T-cells, clouding the picture under the microscope and putting the 2-point maximum for histopathologic findings out of reach. However, as the patient progresses to plaques, tumors, and erythroderma, the proportion of malignant T-cells increases and the diagnosis becomes easier, Dr. Shinohara explained.
In cases where histopathologic uncertainty exists, the immunohistochemistry and molecular studies become particularly important because, when positive, they can raise a patient’s score up to the 4-point diagnostic threshold. Dr. Shinohara focused on recent advances in molecular studies because that’s where the action is of late in the field of MF diagnostics.
High-throughput sequencing and other molecular studies
Three molecular study options are available for the diagnosis of MF: TCR/PCR, which is the traditional clonality study; next-generation high-throughput DNA sequencing; and flow cytometry.
A TCR/PCR study showing a monoclonal T-cell clone on a more subdued polyclonal background is highly suggestive of MF, as opposed to other inflammatory dermatoses. Early in the disease, however, the pattern can be oligoclonal, an inconclusive result. This point is where taking multiple biopsies from different skin sites becomes extremely helpful to amplify TCR/PCR’s sensitivity and specificity. Indeed, investigators at Stanford (Calif.) University have reported that TCR/PCR analysis showing an identical T-cell clone in biopsy specimens from two different skin sites had 82.6% sensitivity and 95.7% specificity for unequivocal MF.
High-throughput sequencing of the T-cell receptor gene has greater specificity for diagnosis of MF than TCR/PCR, and with similar sensitivity.
“The sensitivity of high-throughput sequencing is okay, but really we want it to be helpful in those wishy washy cases where we get an oligoclonal result on TCR/PCR; that’s, I think, an ideal use for it,” Dr. Shinohara said.
In addition to its role in establishing the diagnosis of MF, high-throughput sequencing shows promise for two other potential applications: detection of residual disease following stem cell transplantation and risk stratification in patients with early-stage disease.
Citing a landmark Stanford retrospective cohort analysis of actuarial disease-specific survival in 525 patients with MF and Sezary syndrome, she noted that the majority of patients had stage IA or IB disease – meaning patches and/or plaques on less than or more than 10% of their body surface area – and the survival curves of these patients with early-stage CTCL were flat.
“Most patients are going to live for decades with their disease if they have early disease, and that’s very reassuring for patients,” the dermatopathologist observed.
And yet, early-stage disease does not follow an indolent lifelong course in a subset of patients; rather, their disease becomes aggressive and resistant to all treatments short of stem cell transplantation. Investigators at Harvard University, Boston, have reported that high-throughput sequencing of the T-cell receptor beta gene in lesional skin biopsies is a powerful tool for early identification of this high-risk subpopulation of patients with early-stage MF. They demonstrated in a cohort of 141 patients with early-stage MF, then again in a validation cohort of 69 others, that a tumor clone frequency (TCF) greater than 25% in lesional skin, as measured by high-throughput sequencing, was a more powerful predictor of disease progression than any of the established prognostic factors.
In the discovery set, a TCF in excess of 25% was associated with a 4.9-fold increased likelihood of reduced progression-free survival; in the validation set, the risk was 10-fold greater than in patients with a lesser TCF. These were significantly greater risks than those seen with other proposed biomarkers of diminished progression-free survival, including the presence of plaques; stage IB, as opposed to IA, disease; large-cell transformation; age greater than 60 years; and elevated lactate dehydrogenase levels.
Although this groundbreaking work requires confirmation in another dataset, “this may be something we evolve towards doing in patients with early disease to pick out those who may have bad outcomes later,” Dr. Shinohara commented.
Still, she stressed, molecular studies will never replace histopathologic analysis for diagnosis of MF. “Judicious use of molecular studies may help in establishing the diagnosis, but I don’t think any one molecular study is ever going to be our home run,” she said.
She reported no financial conflicts regarding her presentation.
Global Academy for Medical Education and this news organization are owned by the same company.
Dermatopathologist Michi M. Shinohara, MD, is often asked why it takes so long to diagnose mycosis fungoides. Her reply: Early histopathologic findings in mycosis fungoides (MF) can be subtle, and accurate diagnosis is aided by taking multiple skin biopsies from different sites sequentially over time when there’s diagnostic uncertainty.
“Take multiple biopsies. There is clear literature that taking multiple biopsies from different areas of the body can really increase the sensitivity and specificity of TCR/PCR [T-cell receptor gene PCR clonality studies],” she said at a virtual forum on cutaneous malignancies jointly presented by the Postgraduate Institute for Medicine and Global Academy for Medical Education.
Patients with MF carry multiple subclones, and by taking multiple skin biopsies, different expression patterns may be revealed.
“MF is incredibly mutationally complex, and that has implications for therapy. There is certainly no single, nor even a few, targetable mutations. There are over 50 driver mutations known in CTCL [cutaneous T-cell lymphoma] involving more than a dozen signaling pathways,” said Dr. Shinohara, codirector of the cutaneous lymphoma clinic at the Seattle Cancer Care Alliance and director of dermatopathology at the University of Washington, Seattle.
MF is a lymphoma of skin-resident memory T-cells, the same T-cells involved in the pathogenesis of fixed drug eruption. MF accounts for about half of primary CTCLs. Traditionally, the average time from appearance of skin lesions to definitive diagnosis of MF is 3-6 years.
The International Society for Cutaneous Lymphomas diagnostic algorithm emphasizes that accurate diagnosis of MF requires clinical and histopathologic correlation supported by immunohistochemistry and TCR/PCR or other molecular studies. In an independent validation study, the algorithm demonstrated a sensitivity of 87.5% and specificity of 60% for diagnosis of MF.
Using this algorithm, a diagnosis of MF requires 4 points or more. A maximum of 2 points is available for the key clinical findings of variably sized persistent patches and/or plaques on non–sun-exposed areas, with poikiloderma. Another maximum of 2 points is awarded for the classic histopathologic findings consistent with MF and other forms of cutaneous T-cell lymphoma – namely, a superficial lymphoid infiltrate with epidermotropic but not spongiotic atypia. A positive immunohistochemical study is worth 1 point, and another point is granted for a positive result from a molecular study; both the immunohistochemical and molecular studies should “almost always” be done in patients with suspected MF, whereas a bone marrow biopsy is almost never appropriate.
The challenge for dermatopathologists in making an early diagnosis of MF is that, in patch-stage disease, many of the patient’s own cytotoxic CD8+ T-cells are present in the biopsy specimen battling the malignancy. These tumor-fighting cells often mask the malignant T-cells, clouding the picture under the microscope and putting the 2-point maximum for histopathologic findings out of reach. However, as the patient progresses to plaques, tumors, and erythroderma, the proportion of malignant T-cells increases and the diagnosis becomes easier, Dr. Shinohara explained.
In cases where histopathologic uncertainty exists, the immunohistochemistry and molecular studies become particularly important because, when positive, they can raise a patient’s score up to the 4-point diagnostic threshold. Dr. Shinohara focused on recent advances in molecular studies because that’s where the action is of late in the field of MF diagnostics.
High-throughput sequencing and other molecular studies
Three molecular study options are available for the diagnosis of MF: TCR/PCR, which is the traditional clonality study; next-generation high-throughput DNA sequencing; and flow cytometry.
A TCR/PCR study showing a monoclonal T-cell clone on a more subdued polyclonal background is highly suggestive of MF, as opposed to other inflammatory dermatoses. Early in the disease, however, the pattern can be oligoclonal, an inconclusive result. This point is where taking multiple biopsies from different skin sites becomes extremely helpful to amplify TCR/PCR’s sensitivity and specificity. Indeed, investigators at Stanford (Calif.) University have reported that TCR/PCR analysis showing an identical T-cell clone in biopsy specimens from two different skin sites had 82.6% sensitivity and 95.7% specificity for unequivocal MF.
High-throughput sequencing of the T-cell receptor gene has greater specificity for diagnosis of MF than TCR/PCR, and with similar sensitivity.
“The sensitivity of high-throughput sequencing is okay, but really we want it to be helpful in those wishy washy cases where we get an oligoclonal result on TCR/PCR; that’s, I think, an ideal use for it,” Dr. Shinohara said.
In addition to its role in establishing the diagnosis of MF, high-throughput sequencing shows promise for two other potential applications: detection of residual disease following stem cell transplantation and risk stratification in patients with early-stage disease.
Citing a landmark Stanford retrospective cohort analysis of actuarial disease-specific survival in 525 patients with MF and Sezary syndrome, she noted that the majority of patients had stage IA or IB disease – meaning patches and/or plaques on less than or more than 10% of their body surface area – and the survival curves of these patients with early-stage CTCL were flat.
“Most patients are going to live for decades with their disease if they have early disease, and that’s very reassuring for patients,” the dermatopathologist observed.
And yet, early-stage disease does not follow an indolent lifelong course in a subset of patients; rather, their disease becomes aggressive and resistant to all treatments short of stem cell transplantation. Investigators at Harvard University, Boston, have reported that high-throughput sequencing of the T-cell receptor beta gene in lesional skin biopsies is a powerful tool for early identification of this high-risk subpopulation of patients with early-stage MF. They demonstrated in a cohort of 141 patients with early-stage MF, then again in a validation cohort of 69 others, that a tumor clone frequency (TCF) greater than 25% in lesional skin, as measured by high-throughput sequencing, was a more powerful predictor of disease progression than any of the established prognostic factors.
In the discovery set, a TCF in excess of 25% was associated with a 4.9-fold increased likelihood of reduced progression-free survival; in the validation set, the risk was 10-fold greater than in patients with a lesser TCF. These were significantly greater risks than those seen with other proposed biomarkers of diminished progression-free survival, including the presence of plaques; stage IB, as opposed to IA, disease; large-cell transformation; age greater than 60 years; and elevated lactate dehydrogenase levels.
Although this groundbreaking work requires confirmation in another dataset, “this may be something we evolve towards doing in patients with early disease to pick out those who may have bad outcomes later,” Dr. Shinohara commented.
Still, she stressed, molecular studies will never replace histopathologic analysis for diagnosis of MF. “Judicious use of molecular studies may help in establishing the diagnosis, but I don’t think any one molecular study is ever going to be our home run,” she said.
She reported no financial conflicts regarding her presentation.
Global Academy for Medical Education and this news organization are owned by the same company.
Dermatopathologist Michi M. Shinohara, MD, is often asked why it takes so long to diagnose mycosis fungoides. Her reply: Early histopathologic findings in mycosis fungoides (MF) can be subtle, and accurate diagnosis is aided by taking multiple skin biopsies from different sites sequentially over time when there’s diagnostic uncertainty.
“Take multiple biopsies. There is clear literature that taking multiple biopsies from different areas of the body can really increase the sensitivity and specificity of TCR/PCR [T-cell receptor gene PCR clonality studies],” she said at a virtual forum on cutaneous malignancies jointly presented by the Postgraduate Institute for Medicine and Global Academy for Medical Education.
Patients with MF carry multiple subclones, and by taking multiple skin biopsies, different expression patterns may be revealed.
“MF is incredibly mutationally complex, and that has implications for therapy. There is certainly no single, nor even a few, targetable mutations. There are over 50 driver mutations known in CTCL [cutaneous T-cell lymphoma] involving more than a dozen signaling pathways,” said Dr. Shinohara, codirector of the cutaneous lymphoma clinic at the Seattle Cancer Care Alliance and director of dermatopathology at the University of Washington, Seattle.
MF is a lymphoma of skin-resident memory T-cells, the same T-cells involved in the pathogenesis of fixed drug eruption. MF accounts for about half of primary CTCLs. Traditionally, the average time from appearance of skin lesions to definitive diagnosis of MF is 3-6 years.
The International Society for Cutaneous Lymphomas diagnostic algorithm emphasizes that accurate diagnosis of MF requires clinical and histopathologic correlation supported by immunohistochemistry and TCR/PCR or other molecular studies. In an independent validation study, the algorithm demonstrated a sensitivity of 87.5% and specificity of 60% for diagnosis of MF.
Using this algorithm, a diagnosis of MF requires 4 points or more. A maximum of 2 points is available for the key clinical findings of variably sized persistent patches and/or plaques on non–sun-exposed areas, with poikiloderma. Another maximum of 2 points is awarded for the classic histopathologic findings consistent with MF and other forms of cutaneous T-cell lymphoma – namely, a superficial lymphoid infiltrate with epidermotropic but not spongiotic atypia. A positive immunohistochemical study is worth 1 point, and another point is granted for a positive result from a molecular study; both the immunohistochemical and molecular studies should “almost always” be done in patients with suspected MF, whereas a bone marrow biopsy is almost never appropriate.
The challenge for dermatopathologists in making an early diagnosis of MF is that, in patch-stage disease, many of the patient’s own cytotoxic CD8+ T-cells are present in the biopsy specimen battling the malignancy. These tumor-fighting cells often mask the malignant T-cells, clouding the picture under the microscope and putting the 2-point maximum for histopathologic findings out of reach. However, as the patient progresses to plaques, tumors, and erythroderma, the proportion of malignant T-cells increases and the diagnosis becomes easier, Dr. Shinohara explained.
In cases where histopathologic uncertainty exists, the immunohistochemistry and molecular studies become particularly important because, when positive, they can raise a patient’s score up to the 4-point diagnostic threshold. Dr. Shinohara focused on recent advances in molecular studies because that’s where the action is of late in the field of MF diagnostics.
High-throughput sequencing and other molecular studies
Three molecular study options are available for the diagnosis of MF: TCR/PCR, which is the traditional clonality study; next-generation high-throughput DNA sequencing; and flow cytometry.
A TCR/PCR study showing a monoclonal T-cell clone on a more subdued polyclonal background is highly suggestive of MF, as opposed to other inflammatory dermatoses. Early in the disease, however, the pattern can be oligoclonal, an inconclusive result. This point is where taking multiple biopsies from different skin sites becomes extremely helpful to amplify TCR/PCR’s sensitivity and specificity. Indeed, investigators at Stanford (Calif.) University have reported that TCR/PCR analysis showing an identical T-cell clone in biopsy specimens from two different skin sites had 82.6% sensitivity and 95.7% specificity for unequivocal MF.
High-throughput sequencing of the T-cell receptor gene has greater specificity for diagnosis of MF than TCR/PCR, and with similar sensitivity.
“The sensitivity of high-throughput sequencing is okay, but really we want it to be helpful in those wishy washy cases where we get an oligoclonal result on TCR/PCR; that’s, I think, an ideal use for it,” Dr. Shinohara said.
In addition to its role in establishing the diagnosis of MF, high-throughput sequencing shows promise for two other potential applications: detection of residual disease following stem cell transplantation and risk stratification in patients with early-stage disease.
Citing a landmark Stanford retrospective cohort analysis of actuarial disease-specific survival in 525 patients with MF and Sezary syndrome, she noted that the majority of patients had stage IA or IB disease – meaning patches and/or plaques on less than or more than 10% of their body surface area – and the survival curves of these patients with early-stage CTCL were flat.
“Most patients are going to live for decades with their disease if they have early disease, and that’s very reassuring for patients,” the dermatopathologist observed.
And yet, early-stage disease does not follow an indolent lifelong course in a subset of patients; rather, their disease becomes aggressive and resistant to all treatments short of stem cell transplantation. Investigators at Harvard University, Boston, have reported that high-throughput sequencing of the T-cell receptor beta gene in lesional skin biopsies is a powerful tool for early identification of this high-risk subpopulation of patients with early-stage MF. They demonstrated in a cohort of 141 patients with early-stage MF, then again in a validation cohort of 69 others, that a tumor clone frequency (TCF) greater than 25% in lesional skin, as measured by high-throughput sequencing, was a more powerful predictor of disease progression than any of the established prognostic factors.
In the discovery set, a TCF in excess of 25% was associated with a 4.9-fold increased likelihood of reduced progression-free survival; in the validation set, the risk was 10-fold greater than in patients with a lesser TCF. These were significantly greater risks than those seen with other proposed biomarkers of diminished progression-free survival, including the presence of plaques; stage IB, as opposed to IA, disease; large-cell transformation; age greater than 60 years; and elevated lactate dehydrogenase levels.
Although this groundbreaking work requires confirmation in another dataset, “this may be something we evolve towards doing in patients with early disease to pick out those who may have bad outcomes later,” Dr. Shinohara commented.
Still, she stressed, molecular studies will never replace histopathologic analysis for diagnosis of MF. “Judicious use of molecular studies may help in establishing the diagnosis, but I don’t think any one molecular study is ever going to be our home run,” she said.
She reported no financial conflicts regarding her presentation.
Global Academy for Medical Education and this news organization are owned by the same company.
FROM THE CUTANEOUS MALIGNANCIES FORUM