Abstract

Fibro-osseous pseudotumor of the digits is a conflicting and rare benign lesion leading to serious problems and conflicts in differential diagnosis, especially with extraskeletal osteosarcoma. A 57-year-old man presented with a painful swelling in the proximal phalange of his left index finger. Direct radiography taken on admission revealed a soft tissue swelling with suspicious calcification in the proximal phalange palmar aspect of the index finger of left hand The excised specimen of, 2x1.5x0.7 cm was gray-white with a rough, somewhat irregular outer surface. Microscopic examination revealed a mesenchimal tumorous lesion with a partially degenerated and partially calcified/ ossified myxoid stroma. There were cellular areas composed of fibroblastic spindle cells, with mild-moderate nuclear atypia and moderate mitotic activity. Those cellular areas also contained osteoclast like multinucleated giant cells forming disordered groups. The final diagnosis based on histopathologic, radiographic and clinical findings was fibro-osseous pseudotumor of the digits.