PSAT041 A Rare Case of Severe Cyclical Cushing Syndrome Due to Ectopic ACTH Secretion by Appendiceal Carcinoid

Cushing syndrome (CS) secondary to ectopic ACTH secretion (EAS) is rare and accounts for 10% of CS with majority being bronchial or gut neuroendocrine tumors (NETs) and squamous cell lung cancer. There are only a few case reports of EAS due to appendiceal carcinoid. A 24-year-old woman was referred to endocrinology for 60-pound weight gain, acne, hirsutism, generalized weakness, heat intolerance, and hot flashes. She had secondary amenorrhea for 6 months prior to presentation. Family history was significant for bronchial carcinoid in mother. On examination, she had moon facies, wide purple striae on abdomen, hirsutism, dorsocervical and supraclavicular fat pads. She had normal blood pressure. Her laboratory workup showed potassium 3.2 mmol/L (N, 3.5-5.3), urine free cortisol (UFC) 539 mcg/24 hours (N<50), ACTH 54 pg/ml (N, 6-50) and post 1-mg dexamethasone suppression test cortisol 8.8 mcg/dL. CT abdomen revealed a 3-cm enhancing appendiceal mass, enlarged periappendiceal mesenteric lymph nodes and a 4-cm enhancing right hepatic lobe lesion. Ga-68 Dotatate PET/CT confirmed increased radiotracer uptake in appendiceal mass, lymph nodes and hepatic mass. On liver biopsy, pathology showed well differentiated NET Grade 1 and positive ACTH stain. Repeat UFC was 65 mcg/24 hrs and serum cortisol went down to <1 mcg/dL indicating severe cyclical CS. She was referred to surgical oncology for opinion on debulking surgery. Her genetic testing was negative. She was started on Lanreotide. Given severe cyclical CS with extensive tumor burden, she underwent robotic bilateral adrenalectomy with a plan for cytoreductive surgery once she is on physiologic doses of steroids. Appendiceal NET causing Ectopic CS is exceedingly rare. In 20 years’ experience at NIH, there was only one case of appendiceal NET reported. First reported case was in 1971, when CS was cured by resection of an appendiceal carcinoid incidentally detected on laparotomy for adrenalectomy. There are 3 additional case reports in literature of appendiceal carcinoid with ectopic CS. Management can be challenging particularly in patients with metastatic disease. Medical therapy should be individualized, and adrenalectomy should be considered early in patients with uncontrolled CS due to EAS. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.