Ectopic Cushing's syndrome caused by a well differentiated ACTH-secreting neuroendocrine carcinoma of the ileum.

Cushing's syndrome can be caused by adrenocorticotropic hormone-secreting solid tumors. We report a rare case of an ileal endocrine carcinoma that produced ACTH and induced hypercortisolism. A now 47-year-old man presented at age 41 with weight gain, tremor, perspiration, and general fatigue. Laboratory testing showed hypercortisolism and diabetes mellitus. Further examinations revealed ectopic Cushing's syndrome. The search for the primary tumor was difficult. The patient underwent subtotal thyroidectomy and surgical removal of a pituitary lesion. After resection of an ACTH-producing metastasis of the mesentery, temporary remission of Cushing's syndrome ensued. At the age 45 the primary tumor was detected in the ileum by Ga-68 DOTATOC-PET scan and explorative laparotomy. After surgical removal of this well differentiated neuroendocrine carcinoma the patient significantly improved clinically. He experienced better blood pressure and remission of his diabetes mellitus in addition to increased muscular strength. Endocrine laboratory testing at follow-up examinations confirmed remission of hypercortisolism and diabetes mellitus. A Ga-68 DOTATOC PET scan and a 1 mg dexamethasone suppression test 5 months after surgery showed normal results. Ectopic ACTH secretion within the small bowel is very rare. This case underscores the difficulty in locating the source of ectopic ACTH secretion and suggests using small bowel barium study, tubus endoscopy or video endoscopy for preoperative localization if the small bowel is suspected as tumor source.