Localization of ectopic corticotropin-producing carcinoid tumor with use of indium-111 pentetreotide scintigraphy.

OBJECTIVE: To report on the diagnosis of ectopic corticotropin (adrenocorticotropic hormone [ACTH])-producing bronchial carcinoid tumor by indium-111 pentetreotide (octreotide scan) scintigraphy.
METHODS: We present a case of ectopic ACTH syndrome caused by an occult bronchial carcinoid tumor arising in a lymph node and review the pertinent literature.
RESULTS: Biochemical diagnosis of ACTH syndrome can be difficult, and conventional imaging modalities often do not demonstrate these small carcinoid tumors. After biochemical proof of the presence of ectopic ACTH syndrome in our patient, conventional radiographic studies did not demonstrate any lesions. An octreotide scan showed a lesion in the lung, which was confirmed surgically. ACTH values returned to normal after resection of the lesion, and octreotide scans confirmed the completeness of surgical resection. The carcinoid tumor originated in a lymph node outside the bronchus. The differential diagnosis of ACTH syndrome, the localization of ectopic ACTH-producing tumors, the bronchial carcinoids, and the uniqueness of the carcinoid tumor arising in a lymph node are briefly discussed.
CONCLUSION: Octreotide scintigraphy is useful in localizing occult carcinoid tumors and can be used in the follow-up of patients after successful removal of these tumors.