Bizarre parosteal osteochondromatous proliferation on a phalanx with periosteal erosion

SummaryBizarre parosteal osteochondromatous proliferation (BPOP) is an uncommon benign hand tumor with a high rate of local recurrence, marked proliferative activity, and an atypical histological appearance. The aim of this paper is to present a rare and illustrative example of BPOP with periosteal erosion. A 64-year-old male presented with a 10-year history of a mass, measuring approximately 3 cm in diameter, on the dorsal aspect of the right index finger. On physical examination, the mass was hard, indolent, and located at the level of the proximal phalanx. Roentgenograms displayed a soft tissue mass over the right index finger with erosion of the periosteum. Magnetic resonance imaging revealed a few well-defined lobulated tumors over the right index finger proximal interphalangeal joint with periosteal reaction. The soft tissue tumors were excised and found to have soft consistencies. Pathological findings demonstrated that the tumor was compatible with BPOP. BPOP is a benign but locally aggressive fibro-osseous mass yielding radiographic findings that bear striking clinical similarities to those of other diseases, such as osteochondroma, osteosarcoma, and myositis ossificans. As the radiographic findings of BPOP are equivocal, the differential diagnosis must be based on the pathological results. With this case report, we aim to inform physicians that a hand tumor with an aggressive clinical picture may be benign in origin.