Aberrant Melan-A expression in atypical fibroxanthoma and undifferentiated pleomorphic sarcoma of the skin

Abstract

Aberrant expression of Melan-A and MART-1 in AFX and undifferentiated pleomorphic sarcoma of the skin represents an important diagnostic pitfall with potential for misdiagnosis as melanoma.

Pleomorphic dermal sarcoma: a more aggressive neoplasm than previously estimated

“…There are usually numerous S100 protein‐positive dendritic cells in PDS, but neoplastic cells are consistently negative, allowing its differentiation from melanoma. Focal expression for melan A has been occasionally reported in PDS, but confined to multinucleated giant cells . In addition, spindle cell melanomas can show areas of conventional melanoma or an in situ component, facilitating the diagnosis.…”

Pleomorphic Dermal Neoplasms

“…2,[47][48][49] Importantly, CD34 and v-ets avian erythroblastosis virus E26 oncogene homolog (ERG) are consistently negative in this setting. 44,51,52 The expression of these markers is only focal and largely restricted to tumor giant cells. 3D).…”

“…2,6,12,13 The nomenclature used for these tumors has been confusing, and, in the past, they were often regarded together with AFX. 2,6,12,13,44,[54][55][56] The terms "undifferentiated pleomorphic sarcoma" or "MFH" are, however, problematic as they may easily be mistaken for tumors of deep soft tissue with implication for aggressive disease course and risk for overtreatment. 2,6,13,54 Other terms used include "undifferentiated pleomorphic sarcoma of the skin" or "superficial variant of MFH."…”

Nodule on the forehead

“…The tumours generally express CD10 and CD68, which are nonspecific markers. In a variable number of cases, expression of CNA42 (nonspecific marker for dendritic follicular cells), smooth muscle actin, CD31, epithelial membrane antigen, or Melan A is detected by immunostaining …”

“…In a variable number of cases, expression of CNA42 (nonspecific marker for dendritic follicular cells), smooth muscle actin, CD31, epithelial membrane antigen, or Melan A is detected by immunostaining. 1,3 The features of PDS distinguishing it from AFX include infiltration of the deep subcutis or subjacent tissues, tumour necrosis (in 50% of cases), and perineural or lymphovascular invasion (25% of cases). In addition, PDS usually has poorly delimited and asymmetrical margins.…”