Mediastinal Parathyroid Tumor: Giant Adenoma or Carcinoma?

A 71-yr-old woman presented with progressive weakness, bone pain, polydipsia, and epigastric pain. Laboratory studies established the diagnosis of primary hyperparathy roidism with excessively elevated levels of parathyrod hormone (PTH) complicated by renal failure and anemia. Preoperative imaging using (99m)technetium hexakis 2-methoxy-isobutylisonitrile (MIBI) demonstrated an area of intense uptake in the mediastinum, which on T(2) -weighted magnetic resonance imaging revealed the presence of a hyperintense mediastinal mass of 25 mm in diameter adjacent to the ascending aorta Surgical exploration and resection of the mass were performed, and histological examination of the tumor revealed solid 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 markedly positive immunoreactivity of tumor cells for p53 protein and absence of nuclear immunoreactivity for the retinoblastoma tumor-suppressor 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 parathyroid neoplasia.