Osteoblastoma

Osteoblastoma is an uncommon benign bone-forming neoplasm that accounts for about 1% of all primary bone tumors and 1 to 5 % of all benign bone tumors, and 10% of all osseous spinal neoplasms. Historically it was referred to as giant osteoid osteoma highlighting its histopathologic similarities to osteoid osteoma. In fact, some authors consider the entities to be variant expressions of the same pathologic process; however, the prevailing opinion is that they are distinct pathologic entities with varying clinical presentations. Osteoblastoma commonly arises in the posterior elements of the spine and the sacrum (approximately 30 to 40%). Other common locations include the mandible (referred to as cementoblastoma) and long tubular bones (lower > upper extremities), where it is usually observed in the metadiaphysis. An accurate diagnosis of osteoblastoma is critical in determining the appropriate treatment modality and prognosis.  In most cases, the basis for diagnosis is from clinical, radiological, and mainly histopathological examination. Osteoblastoma has a variable radiologic appearance ranging from indolent to very aggressive. In general, osteoblastoma has a good prognosis, and patients are often cancer-free after surgical treatments of intralesional curettage or marginal en bloc resection. In cases that are not amenable to surgical excision, radiotherapy can be performed. In cases with more aggressive imaging and/or clinical features, distinction from aggressive (epitheliod) osteoblastoma or osteoblastoma-like osteosarcoma, two borderline osteoblastic tumors, is necessary. In rare cases, osteoblastoma can be associated with systemic symptoms such as fever, weight loss, and diffuse periostitis, referred to as toxic osteosarcoma.