Osteoblastoma

Osteoblastoma is an osteoid producing benign bone lesion which can demonstrate
aggressive clinical behavior.

The foot is the 3rd most common location of osteoblastoma after the spine and the femur. 12.5% of osteoblastoma occur in the bones of the foot. The mean age of the patient is about 22 years.

Most occur in the hind foot, and the talus is most commonly affected bone. In one review of 41 osteoblastomas in the foot, two evolved into malignant sarcomas.

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.

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.

Careful correlation of the clinical, radiological, and histological information is required in order to determine the correct treatment. There is a lack of consensus as to what histological characteristics are associated with more or less aggressive
behavior. (temple, izel, FAI 1998:698)

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.

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