Florid Reactive Periostitis of the Clavicle: A Case Report.

Florid reactive periostitis (FRP) is a rare benign fibro-osseous proliferation, occurring mostly in the short tubular bones of hands and rarely in the long tubular bones. We report a surgically confirmed case of FRP involving the clavicle in a 26-year-old male. On MRI scans, a soft tissue mass with T2 high signal intensity was found that originated from the periosteum of the clavicle and included surrounding a periosteal elevation and perilesional soft tissue edema. Strong contrast enhancement was noted inside the mass and along the periosteum involving more than half of the circumference of the clavicle. Serial radiographs revealed a soft tissue mass without mineralization that turned into an ossified mass with a solid periosteal reaction within a month.