Osteosarcoma associated with hyperparathyroidism.

The fourth case in the literature is presented of a patient with the rare association of hyperparathyroidism and osteosarcoma. A 56-year-old woman presented with hyperparathyroidism and a lesion in the tibia. Initial diagnosis was brown tumor. Histology, however, revealed osteosarcoma, and the patient was treated accordingly. The experimental induction of osteosarcoma by parathormone in rodent studies makes this finding alarming, considering the increasing use of parathormone in the treatment of osteoporosis. The mechanism by which osteosarcoma is induced in humans cannot be explained based on current knowledge of mechanisms of action of parathyroid hormone.