Osteoblastoma is a solitary, benign and self-limited tumor that produces osteoid and bone. The tumor occurs in the dorsal aspect of vertebrae, the metaphysis or diaphysis of long bones, and rarely in the pelvis. In the
spine, the tumor is usually located in the posterior processes while the vertebral bodies are spared. The differential diagnosis of osteoblastoma includes osteoid osteoma, osteosarcoma, giant cell tumor and aneurysmal bone cyst.
The common symptoms are pain of long duration, swelling and tenderness. Tumors of the spine can cause scoliosis and neurological symptoms.
On x-ray, osteoblastomas appear as a radio-lucent defect with a central density due to ossification. The lesion is well circumscribed and may have a surrounding sclerosis. The tumor demonstrates increased isotope
uptake on bone scan.
     On gross examination, osteoblastomas are red to tan in color with hemorrhagic areas. The compact tissue is granular, friable and gritty. Hyperemia is particularly evident in the spongy bone of vertebrae, ribs and the pelvis.
     The classic microscopic finding of osteoblastoma is irregular spicules of mineralized bone and eosinophilic osteoid rimmed by osteoblasts. The vascular stroma is characterized by pleomorphic spindle cells. The tumor cells differentiate into osteoblasts which make varying amounts of osteoid and woven bone. Cartilage production is a very rare finding in an osteoblastoma and should raise the suspicion of osteosarcoma.
     A biopsy is usually performed to confirm the diagnosis. Surgical resection by curettage, intralesional excision or en-bloc excision are all treatment options depending on the site. Cryosurgery, radiation and chemotherapy may have a role in aggressive and surgically unresectable lesions of the spine.

Osteoblastoma vs. Osteoid Osteoma
inconsistent pain  vs.persistent, nocturnal pain
irregular tissue pattern vs. regular pattern
>2 cm vs. < I cm

Bullough, Peter, Orthopaedic Pathologv (third edition), Times Mirror International Publishers Limited: London, 1997.

Gitelis S., R. Wilkins and EU Conrad, Benign Bone Tumors. Instructional Course Lectures, 45:425-46, 1991.

Huvos, Andrew, Bone Tumors: Diagnosis. Treatment and Prognosis, W.B. Saunders Co., 1991.

Ruggieri, P., RA McLeod, KK Unni and FH Sim, Osteoblastoma, Orthopedics, 19(7):621-4, July 1996.









831 Beacon Street #130

Newton Center, Massachusetts 02459