Cushing's disease: results of transsphenoidal microsurgery with emphasis on surgical failures.

From 1977 to 1988, 56 patients with a preoperative diagnosis of Cushing's disease were treated by transsphenoidal microsurgical exploration of the pituitary gland. In 42 patients, a discrete tumor was found and a selective adenomectomy was performed. Total hypophysectomy was performed in nine patients. In an attempt to preserve pituitary function, a technique of subtotal hypophysectomy was utilized in the remaining five patients. Regular and adequate follow-up results were obtained in 53 patients. A sustained remission was obtained in 45 of these 53 patients for a remission rate of 84.9%. Eight patients were classified as therapeutic failures. The causes for failure included: 1) invasive tumor; 2) hyperplasia mistaken for an adenoma; 3) a presumed ectopic source of adrenocorticotropic hormone; 4) misdiagnosis; 5) atypical tumor; and 6) recurrence of disease after remission. In cases of therapeutic failure, the original diagnosis of Cushing's disease must be reevaluated and treatment continued until sustained remission is achieved. Necessary measures to help avoid surgical failures and an approach for further diagnostic and therapeutic maneuvers in these cases are discussed.