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

The overwhelming majority of cutaneous neoplasms with melanocytic differentiation are nevi, melanomas, or less commonly 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. The ones 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.