Parosteal osteosarcoma of the thumb metacarpal: a case report.

A 60-year-old man presented with increasing swelling of his right thumb, duration one year. Imaging studies demonstrated a bone-forming lesion extending from the dorsal cortex of the thumb metacarpal and involving the underlying medullary canal. Incisional biopsy yielded the diagnosis of parosteal osteosarcoma. The differential diagnosis for and rarity of parosteal osteosarcoma arising in the tubular bones of the hand are discussed.