Multicentric giant cell tumor of bone.

Giant cell tumor of bone accounts for 4% to 5% of primary bone tumors in the United States. Multicentric giant cell tumors occur in < 1% of all patients with giant cell tumors, and only 43 patients with multicentric giant cell tumor have been reported on in the literature. This series presents 3 additional cases of multicentric giant cell tumor, includes updated data for 2 patients previously reported on in the literature, and reviews 24 cases previously reported on in detail in the literature. The mechanism by which giant cell tumor involves multiple locations is not known. Multicentric giant cell tumor, in contrast to unifocal giant cell tumor, has a tendency to involve the hands, feet, and metaphysis/diaphysis of long bones and to occur in a slightly younger population. In 15 of the 29 patients reviewed, a second lesion did not develop for > 2 years after their initial presentation. Eighteen of those 29 patients had > 2 sites of tumor involvement, 1 of whom had 11 lesions. Two of the 5 patients in the authors' series presented with a spectrum of disease activity, with latent, active, and aggressive lesions present throughout the observation period.