MEDIASTINAL PARATHYROID TUMOR - GIANT ADENOMA OR CARCINOMA

A 71-yr-old woman presented with progressive weakness, bone pain, poly dipsia, and epigastric pain. Laboratory studies established the diagno sis of primary hyperparathyroidism with excessively elevated levels of parathyroid hormone (PTH) complicated by renal failure and anemia. Pr eoperative imaging using (99m)technetium hexakis 2-methoxyisobutylison itrile (MIBI) demonstrated an area of intense uptake in the mediastinu m, which on T-2-weighted magnetic resonance imaging revealed the prese nce of a hyperintense mediastinal mass of 25 mm in diameter adjacent t o the ascending aorta. Surgical exploration and resection of the mass were performed, and histological examination of the tumor revealed sol id masses of epithelial cells growing in a trabecular pattern, hyaline bands, and low mitotic activity. Immunohistochemical staining of the tumor specimens using monoclonal mouse antihuman antibodies revealed m arkedly positive immunoreactivity of tumor cells for p53 protein and a bsence of nuclear immunoreactivity for the retinoblastoma tumor-suppre ssor protein, findings consistent with parathyroid carcinoma. Improved imaging techniques and advances in molecular pathology of parathyroid disorders may help to improve clinical management of patients with pa rathyroid neoplasia.