Osteoblastoma is a rare bone tumor associated with osteoid and atypical bone formation. We describe a case of osteoblastoma of the mandible in a 19-year-old woman. Radiographic examination of the tumor showed a well-defined radiopaque region, measuring approximately 13 mm in diameter and surrounded by a radiolucent area. The treatment was complete surgical excision. The postoperative course was uneventful. The osteoblastoma was mainly composed of abundant connective tissue showing active angiogenesis and osteoid bone covered with osteoblast-like cells and osteoclast-like multinuclear giant cells. We studied the tumor histologically and ultrastructually and examined tumor cell proliferation with MIB antibody immunohistologically.
