Osteoid Osteoma

Abstract

Benign osteoid and bone-forming tumor which has limited growth potential, with classic pain symptomatology, and consists of a small core or nidus – less than 2 cm in diameter – surrounded by a typical conspicuous zone of reactive sclerotic bone. It has a high incidence – 12 % of all benign tumors. It is more frequent in males, and 50 % of patients are in the second decade. Seventy percent arise in tubular bones – most frequently the upper end and lower end of the femur, tibia, and humerus. Fifteen percent occur in the spine in the posterior elements. Pain is the classic symptom – more intense at night and relieved dramatically by aspirin. Roentgenographic appearance of the nidus is characteristic, round or oval surrounded by sclerosis. Twenty-five percent present with mineralization of the central area. They may arise in cortical, subperiosteal, or medullary areas. CT is the most useful method to show the nidus. The bone scan shows an extremely hot spot. Histologically the nidus is composed of haphazard anastomosing immature osteoid and bone trabeculae lined by uniform osteoblasts and a few multinucleated giant cells. The bone marrow is composed of a loose fibrovascular stroma. The prognosis is excellent. Percutaneous radiofrequency ablation is the treatment of choice and in the spine, excision.