BACKGROUND. An asymptomatic rib lesion was discovered by means of a bone scan obtained during the clinical evaluation of an adult man with biopsy proven prostate adenocarcinoma. Clinically and radiologically considered to be a metastatic focus, on resection it proved to be an osteoid osteoma (00). METHODS. A review of the English medical literature on 00 was conducted with emphasis on the occuence in older patients, costal location, and the absence of pain. RESULTS. 00 in patients older than age 50 years is rare (1%-2% of cases). Only 18 cases of painless 00 were found. Of these, 8 (44%) occurred in the phalanges, and 3 (17%) in the cranial-facial bones, both uncommon sites for 00; only 7 (39%) arose in the long bones, the most common site for conventional 0 0 . A disproportionate number of these patients (44%) were younger than age five years, a rarity for 00. Fourteen reported examples of costal 00 were found, all of which were associated with pain. The possible mechanisms involved in the production of pain, including analysis of the effect of its site of origin and the presence of nerve fibers, is reviewed.
CONCLUSIONS.
Costal 00 is distinguished from osteoblastoma and from what has been described as painless fibro-osseous lesion of the rib. The infrequency of metastases as a cause of solitary rib lesion is emphasized. Cuncer 199s; 721442-9.