Osteogenic melanoma.

A case of osteogenic melanoma arising in the sole of the foot of a 75-year-old male is described. The patient had a history of cutaneous malignant melanoma of the left sole from 15 years previously with local recurrence 5 years previously. A second recurrence presented as an unencapsulated, poorly circumscribed mass measuring 7.5x6x3 cm, located in the dermis, subcutis and muscle, and composed of a lobular growth of malignant osteocartilaginous elements with foci of epithelioid cells. The tumor was strongly positive for HMB45 and S-100 protein. No conventional melanoma was found in the skin. The patient had no evidence of recurrence or metastasis 10 months after surgery. Pathologists and clinicians should be aware of the existence of osteogenic melanoma and should differentiate it from mimics.