Pulmonary arterial sampling was useful for localizing ectopic ACTH production in a patient with bronchial carcinoid causing Cushing syndrome.

OBJECTIVE: We report a 44-year old man with ectopic adrenocorticotropic hormone (ACTH) syndrome caused by bronchial carcinoid that developed Cushing syndrome.

METHODS: We performed several imaging studies, including chest and abdominal CT, for exploration of nodules and selective pulmonary arterial sampling for localizing a source of ectopic ACTH production.

RESULTS: The patient was diagnosed as Cushing syndrome due to ectopic production of ACTH without identification of its source(s). After 2 years' follow-up with repeated CT scans every 6-12 months and treatment with metyrapone, chest CT revealed two small nodules respectively in the segment (S) 4 and 10 of the right lung. We performed selective pulmonary arterial sampling from branches of the right pulmonary artery to obtain blood from the nodules in a reverse flow fashion: wedged sampling from the basal branch (A8, 9 and 10) revealed significant elevation of ACTH, whereas sampling from the lateral branch (A4) did not, indicating that the S10 nodule produced ACTH ectopically. The video-assisted thoracoscopic surgery removing the right inferior lobe normalized plasma ACTH, serum cortisol and 24-hour urinary free cortisol. The S10 nodule was histologically diagnosed as atypical bronchial carcinoid containing immunoreactive ACTH.

CONCLUSIONS: Selective pulmonary arterial sampling was useful for localizing the lesion of ectopic ACTH production and helped make the decision for its surgical removal. This procedure should be considered once lung nodules suspicious for ectopic ACTH production are identified in patients with EAS.