OSTEOID OSTEOMA - THE UNIQUELY INNERVATED BONE-TUMOR

Osteoid osteomas are benign bone-forming tumors that despite their sma ll size (<2.0 cm) characteristically produce severe nocturnal bone pai n that is relieved by aspirin. This typical clinical presentation is v irtually unique among bone tumors, Histologically, osteoid osteomas ar e circumscribed nodules of woven bone and osteoid with prominent osteo blastic rimming (the nidus), surrounded by thickened cortical and trab ecular bone and loose fibrovascular tissue (the reactive zone), Prosta glandins mediate the pain of osteoid osteomas, but there have been few studies of their innervation, We investigated 34 osteoid osteomas usi ng a streptavidin immunohistochemical technique and a panel of antibod ies to neural and neural-associated antigens (phosphorylated neurofila ment, neurofilament, and S-100 protein), Whenever possible, sections o f the nidus and the reactive zone were stained, As controls, we staine d other bone tumors that can be painful, including 10 osteoblastomas, 5 osteosarcomas, 6 giant cell tumors, 4 chondroblastomas, 3 aneurysmal bone cysts, and 6 cases of fibrous dysplasia, Twenty-five osteoid ost eomas contained phosphorylated neurofilament-, neurofilament-, and/or S-100-positive nerve fibers in the reactive zone around the nidus and/ or in the nidus, The nerve fibers were larger and more abundant in the reactive zone than in the nidus, and they were occasionally visible o n hematoxylin-and eosin-stained slides on retrospective review, The sm aller nerve fibers within the nidi were never identified, even after e xtensive review of those slides. In the nine cases in which nerve fibe rs were not identified.