Abstract

Fibro-osseous pseudotumor of the digits is a heterotopic ossification closely related to myositis ossificans and occurs in the subcutaneous tissue of the digits. This lesion is considered a reactive fibroblastic proliferation with metaplastic bone formation. We report a case of fibro-osseous pseudotumor of left index finger in a 28-year-old woman. She had had an ovoid smooth subcutaneous mass with tenderness on the left index finger for one month. In gross, the specimen consisted of a relatively circumscribed, rubbery soft mass with grayish white cut surface measuring 2.0 1.7 1.5 cm. Upon microscopic examination the lesion showed irregular multinodular growth with considerably variable cellularity. Because of the focal hypercellularity, cellular atypia, and increased mitotic activity this lesion may be confused with extraskeletal osteosarcoma or parosteal osteosarcoma. This rare lesion is curable by complete local excision.

• Keywords: Fibro-osseous pseudotumor;Soft tissue;Digits