Osteoma of the innominate bone with intraosseous and parosteal involvement

A case has been presented of a 47-year-old woman with a dense bony mass both within and on the surface of her right public ramus. This was discovered incidentally on plain radiographs of the pelvis. Besides osteoma, a differential diagnosis of parosteal osteosarcoma, ossifying parosteal lipoma, periostitis ossificans, osteochondroma with attenuated cartilage cap, and melorheostosis was considered. Histological evaluation of open biopsy samples showed typical findings of an osteoma. This is an unusual case of an osteoma with both parosteal and intraosseous involvement.