RESUMO
Osteoblastoma is a slow-progressing, benign bone tumor, that is not frequently observed in clinical orthopaedics (approximately 1% of all primary bone tumors). There is predilection for the vertebrae (posterior arch), the femur, the tibia, and the cranium; it affects young subjects (from 10 to 35 years), with predilection for males (males: females = 2:1). Symptoms are not very specific, characterized essentially by moderate, discontinuous pain, that is responsive to treatment by NSAIDS; it may, at times, be asymptomatic. On radiographic assessment it is viewed as a lytic area that is rounded, greater than 2 cm in size, with unclear margins, with or without peripheral bone reaction. It is not easy to diagnose osteoblastoma, particularly if it is localized in unusual sites, such as in the pelvis. The authors present a case of osteoblastoma of the acetabular bottom in a subject aged 22 years, that was not diagnosed unrecognized for about 2 years from the onset of symptoms.
