Use of In-111 pentetreotide scintigraphy in the diagnosis of a midgut carcinoid causing Cushing's syndrome.

A 57-year-old man presented with clinical features of hypercortisolism and was diagnosed with ACTH-dependent Cushing's syndrome. Biochemical testing showed partial suppression of urinary free cortisol with high dose dexamethasone. Initial computed tomography (CT) of the chest and abdomen, and magnetic resonance imaging of the pituitary were negative. In-111 pentetreotide scintigraphy with single photon emission computerized tomography revealed two 'hot' lesions in the abdomen which were then confirmed by subsequent directed thin-slice abdominal CT and small bowel barium study. At surgery, two segments of ileum, adjoining mesentery and lymph nodes were resected. Histopathology was consistent with a malignant carcinoid tumor of the ileum which stained intensely for ACTH. Plasma ACTH, and serum and urinary cortisol normalized postoperatively. To our knowledge, this is the first reported case of ileal carcinoid tumor causing Cushing's syndrome with premortem diagnosis. Another unique feature of this case is that In-111 pentetreotide scan provided the decisive clue to localization of the tumor.