Subcutaneous pigmented clear cell sarcoma as a challenging simulator of melanoma

Nevus, melanoma or something else? Mesenchymal neoplasms with melanocytic differentiation

The overwhelming majority of cutaneous neoplasms with melanocytic differentiation are nevi, melanomas and more rarely melanocytomas. Nevertheless, there is also a group of mesenchymal neoplasms with genuine melanocytic differentiation which can create diagnostic difficulties with significant repercussions. These can rarely present as primary or metastatic cutaneous lesions. Theones that are relevant to a dermatopathologist include malignant melanotic nerve sheath tumor, perivascular epithelioid cell neoplasm and clear cell sarcoma. This work will provide a thorough review of clinical presentation, morphologic and immunohistochemical features as well as molecular pathogenesis of these tumors. We hope to familiarize the general dermatopathology readership with a group of neoplasms of mesenchymal lineage exhibiting melanocytic differentiation and ultimately avoid diagnostic misadventures. This article is protected by copyright. All rights reserved.

Superficial Clear Cell Sarcoma (Melanoma of Soft Parts) of the Large toe in an 80-Year-Old Female With a Rare Cytogenetic Translocation

We present a case of clear cell sarcoma (CCS) on the left large toe of an 80-year-old female. CCS, also known as “melanoma of soft parts,” is a rare soft tissue neoplasm that exhibits melanocytic differentiation. Most cases occur on the distal extremities of young female adults. CCS shares histopathologic and immunohistochemical features with malignant melanoma that cause diagnostic difficulties distinguishing between these entities; therefore, cytogenetic studies of specific translocations are paramount in obtaining the correct diagnosis. The majority of CCS cases reveal a t(12;22)(q13;q12) EWSR1/ATF1 translocation, while a rare subset of CCS demonstrate a t(2;22) (q32:q12) EWS/CREB1 translocation. Our patient presented with a 50-year history of a nodule on the dorsum of her left large toe, with increasing size and tenderness over the past nine months. Histopathology and immunoperoxidase staining indicated CCS as a differential diagnosis. Cytogenetic analysis revealed a translocation in t(2;22) (q32;q12) resulting in the EWSR1/CREB1 gene, confirming a diagnosis of CCS. The translocation, histologic location, and long-standing clinical course exhibited in this case are exceptionally rare, and we hope to inform dermatologists of an uncommon presentation of CCS in an unexpected age group.