Appearance of a thymic mass after treatment of Cushing's syndrome.

A 23-year-old woman was referred to our center with hirsutism, acne, weight gain, weakness, and irregular menses. Laboratory tests revealed increased levels of cortisol and sex hormones, and reduced adrenocorticotropic hormone levels. The patient underwent a right adrenalectomy. Pathology of the resected right adrenal gland showed an adrenal carcinoma. Computed tomography 8 months after the surgery revealed a thymic mass that was not detected preoperatively. The frequency of rebound thymic hyperplasia after normalization of hypercortisolism is not known, but possibly as high as 40%. Physicians must be aware of this phenomenon to avoid unnecessary thoracic surgery.