Carcinoid tumors: CT and I-131 meta-iodo-benzylguanidine scintigraphy

The diagnostic value of computed tomography (CT) and iodine-131 meta-iodo-benzylguanidine (MIBG) scintiscanning was studied in nine patients with histologically proved carcinoid tumors of intestinal (n = 4), bronchial (n = 3), or thymic (n = 2) origin. CT scans clearly depicted the tumors and metastases in relation to surrounding vital structures but did not provide findings specific for carcinoids. The appearance on CT of an abdominal soft-tissue mass with a radiating pattern of linear densities was found to be highly suggestive of intestinal carcinoid tumors. I-131 MIBG scintiscans disclosed intense tracer uptake in the tumors and metastases in five patients. MIBG studies correctly depicted nine of nine tumor manifestations in intestinal carcinoids and four of six tumor manifestations in bronchus carcinoids. No MIBG concentration was found in thymus carcinoids. Because of its selective uptake mechanism, I-131 MIBG scintigraphy can allow specific detection and localization of neuroendocrine tumor tissue in patients with suspected carcinoid tumors. MIBG scintigraphy has diagnostic potential as a screening procedure in carcinoid tumors, especially those of intestinal origin.