Subungual melanoma with osteocartilaginous differentiation.

Osteocartilaginous metaplasia is known to occur rarely in melanomas, particularly in subungual melanomas. We present a case of a calcified subungual soft tissue tumour in which biopsy of the lesion showed malignant round and spindle-shaped tumour cells, many of which were associated with the formation of cartilage and osteoid-like material. Subsequent resection showed clear histological evidence of a subungual melanoma. Tumour cells expressed S100, melan-A and neurone-specific enolase but were negative for HMB45. Diagnostic radiological and histological features and the nature of the osteocartilaginous differentiation within this lesion is discussed.