[Differential diagnosis in a case of brown tumor caused by primary hyperparathyroidism].

Fibrous-cystic osteitis is a bone metabolic disorder related to hyperparathyroidism. This pathological condition shows a bone catabolism enhancement, due to increased level of PTH. Brown tumour is a uni- or multi-focal bone lesion, which represents the terminal stage of the hyperparathyroidism-dependent bone pathology. This focal lesion is not a real neoplasm showing itself as a cellular reparative process, mainly interesting the jaws, specially the mandible. Because of the similar radiological features (cyst-like radiolucency) showed by other lesions, the diagnosis can be difficult. Histology cannot guarantee a certain diagnosis, some lesions, such as giant cell tumour, giant cell granuloma, aneurysmal bone cyst and cherubism, show a similar macroscopical and microscopical features. Differential diagnosis is possible only by comparative evaluation of clinical, radiological and biochemical evidences. Personal experience with a patient affected by maxillary expansive lesion previously diagnosed as GCT is reported. Radiological examinations showed another cyst-like lesion involving the mandible. Clinical history and multifocality of lesions were suggestive for the presence of a systemic disease, laboratory data allowed a primary hyperparathyroidism diagnosis. Parathyroid scintigraphy was performed and detected a parathyroid adenoma. In first instance the patient underwent to surgical operation on the jaws in order to stop the rapid progression of bone lesions, and then another operation for the removal of parathyroid adenoma was performed.