Malignant melanoma with osteocartilaginous differentiation.

We report a case of acral lentiginous melanoma on the plantar aspect of foot in a 50-year-old male that exhibited a prominent osteo-cartilaginous differentiation in the metastatic inguinal lymph node. The ability of melanomas to undergo multidirectional differentiation leads to a variety of histological appearances that can be misleading. Although the true nature of the tumor is most often recognized at the primary cutaneous site, metastatic tumors may closely mimic other malignant mesenchymal or neuro-ectodermal tumors. Hence awareness of this unusual phenomenon occurring in malignant melanoma is essential to avoid misdiagnosis.