Ectopic ACTH-producing pheochromocytoma in a patient with an APC gene mutation: A case report

ACTH-producing pheochromocytomas are rare. Familial adenomatous polyposis (FAP), caused by mutations in the Adenomatous Polyposis Coli (APC) gene, increases the risk of colorectal neoplasia, as well as adrenal lesions. This is the case of a 21-year-old male presenting with a 10cm right adrenal mass and rapidly progressive Cushing's syndrome (CS). Biochemical workup confirmed ACTH-dependent CS and catecholamine excess and a ⁶⁸Ga-DOTA-NOC PET/CT showed SSR expression limited to the adrenal mass. Methyrapone and alpha/beta blockade were initiated, followed by right adrenalectomy. Histopathology confirmed an ACTH-secreting pheochromocytoma (pheochromocytoma of the adrenal gland scaled score - PASS: 16; grading system for adrenal pheochromocytoma and paraganglioma - GAPP: 8). A truncating germline mutation in the APC gene (c.6189_6190del) was detected, associated with attenuated FAP. This is, to our knowledge, the first case ever reported of an ACTH-producing pheochromocytoma in a patient with an APC gene mutation. This case raises the possibility of a broader phenotypic spectrum in FAP and highlights the importance of vigilance for unusual tumor presentations in hereditary cancer syndromes.