Systemic syndromes frequently associated with mediastinal tumors include:

A. Myasthenia gravis.

B. Hypercalcemia.

C. Malignant hypertension.

DISCUSSION: Myasthenia gravis occurs in 10% to 50% of patients with thymoma. The incidence with which myasthenia gravis occurs in patients with a thymoma increases with the age of the patient. In males over 50 and females over 60 years of age, the incidence appears to be greater than 80%. Hyperparathyroidism due to a mediastinal parathyroid adenoma is a cause of hypercalcemia. Although parathyroid glands may occur in the mediastinum in 10% of the patients, they are usually accessible through a cervical incision. A sternotomy is required infrequently, even in those patients with a mediastinal parathyroid gland. Most often the adenomas are found embedded in or near the superior pole of the thymus. Mediastinal paraganglioma may produce significant catecholamines, predominantly norepinephrine. Catecholamine production causes a classic group of symptoms associated with pheochromocytomas, including periodic sustained hypertension often accompanied by orthostatic hypotension, and hypermetabolism manifested by weight loss, hyperhydrosis, palpitation, and headaches. Mediastinal carcinoid tumors have been more frequently associated with Cushing's syndrome because of the production of adrenocorticotrophic hormones. These tumors uncommonly cause the carcinoid syndrome.