Giant cell tumor of skin.

Giant cell tumor of the skin is a rare entity showing gross and histological features similar to those of giant cell tumor of the bone. We report a case of malignant giant cell tumor of the thigh in a 55-year-old man. Histological features showed a biphasic population of mononuclear cells admixed with osteoclast-like giant cells. The nuclei of the giant cells were similar to those of the mononuclear cells. This tumor should be distinguished from a variety of cutaneous neoplasms that contain multinucleated giant cells.