Comment on primary localization of an ectopic ACTH-producing bronchial carcinoid tumor by indium111 pentetreotide scintigraphy.

Abstract

Torpy et al. (1) and Tabarin et al. (2) reported recently a low diagnostic sensitivity of Indium pentetreotide scintigraphy as a tool for the localization of ectopic ACTH-producing tumors. de Herder and Lamberts in their editorial comment (3) suggested that, despite these negative results, Indium pentetreotide scintigraphy could be helpful in a minority of patients with Cushing’s disease and should be used in the localization procedure of ectopic ACTH sources. We would like to emphasize this view with a short case report of a recent patient in whom Indium pentetreotide scintigraphy remained the only procedure to localize an extremely small ACTH-producing bronchial carcinoid. A 37-yr-old male patient was admitted with hypokalemic hypertension, muscle weakness, hyperglycemia, weight gain, facial swelling, and psychosis. The diagnosis of ACTH-dependent Cushing’s syndrome was established. Plasma ACTH and cortisol concentrations were unresponsive to corticotropin releasing CRH hormone and high dose dexamethasone, suggesting ectopic Cushing’s syndrome. The diagnosis was confirmed by inferior sinus petrosal catherterization, which demonstrated no gradient between the pituitary and the peripheral ACTH levels. Computed tomography (CT) and magnetic resonance imaging (MRI) of chest and abdomen did not visualize the ectopic ACTH source. Adrenostatic treatment was introduced but failed to control hypercortisolism. The patient underwent bilateral adrenalectomy. The postoperative period was uneventful, and the patient recovered from Cushing’s syndrome. At follow-up, plasma ACTH concentrations were steadily increasing, suggesting tumor progression, but CT and MRI scans of the chest and the abdomen after 3, 6, and 9 months did not identify the ectopic ACTH source. Indium pentetreotide scintigraphy scanning with 214 Mbq Indium octreotide was performed, revealing a spot in the left lung 24-h post-injection (Figs. 1 and 2). In spite of this finding, CT (2 mm slices) and MRI were still unable to localize the tumor. Exploratory thora-