[The brown tumour in untreated hyperparathyroidism].

The brown tumour (osteitis fibrosa cystica) is a rare, non-neoplastic, expansively growing lesion containing giant cells. Hyperparathyroidism (hyperparathyroidism [HPT]) leads to the development of a brown tumour in 2 to 3 percent of cases. This can manifest itself in any part of the skeleton.