Subungual malignant melanoma with cartilaginous differentiation.

A case of subungual malignant melanoma with cartilaginous differentiation is presented and the phenomenon of sarcomatoid differentiation in malignant melanoma reviewed. Osseous and/or cartilaginous (osteocartilaginous) differentiation of malignant melanoma is rare. Only 14 cases have previously been reported. This small number of cases and the subject of this Case Report have several features in common, including acral (particularly subungual) location, high Breslow thickness, presence of a lentiginous radial growth phase component, and predominance of epithelioid melanocytes with amelanotic cytoplasm. Melanoma with osteocartilaginous differentiation may therefore represent a subgroup of melanoma with distinctive clinical and pathologic features. Further study is required to establish whether any unique molecular or genetic features are also present.