[Functional mediastinal parathyroid adenoma with cystic change; report of a case].

We report a case of functional mediastinal parathyroid adenoma with cystic change. A 72-year-old woman was admitted to our hospital because of general fatigue. Laboratory examinations suggested a diagnosis of hyperparathyroidism (HPT) based on high levels of serum calcium and intact parathyroid hormone (PTH). Computed tomography (CT) revealed the shape of a cystic tumor with a diameter of 4 cm in the anterior mediastinum. 99mTc-MIBI scintigraphy showed accumulation of the radioisotope in the tumor. The patient was diagnosed as primary HPT caused by the cystic parathyroid adenoma. The tumor was resected through a median sternotomy. The patient had an uneventful postoperative course, and her serum calcium and intact PTH levels rapidly returned to normal. Careful dissection is essential in order not to occur implantation of parathyroid tissue.