A misdiagnosed melanoma: a case of cutaneous epithelioid malignant peripheral nerve sheath tumor

Malignant Peripheral Nerve Sheath Tumor (MPNST) is a rare soft tissue sarcoma that can occur in superficial locations. Histologically it is categorized into two variants: a conventional/spindled and an epithelioid variant. The latter one is very rare and can be confused histologically with malignant melanoma as it is diffusely positive for S100-protein. Herein we present a case that was initially misdiagnosed as malignant melanoma and discuss morphological and immunohistochemical clues to reach a correct diagnosis.