8604 Ectopic Cushing’s Syndrome Associated with a Metastatic Pancreatic Mixed Neuroendocrine Non-neuroendocrine Neoplasm (MiNEN) with Amphicrine Features

Abstract Disclosure: A. DeMarsilis: None. C. Jiang: None. O. Lavrynenko: None. D. Motavalli: None. C. Musurakis: None. Z.H. Taxin: None. E.D. Rosen: Advisory Board Member; Self; Source Bio, Inc.. Consulting Fee; Self; Novartis Pharmaceuticals, Gensaic. M.S. Irwig: None. Background: Ectopic Cushing’s Syndrome (CS) makes up 9-18% of ACTH-dependent CS cases, of which fewer than 15% are attributed to pancreatic neuroendocrine tumors (1). Mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) are rare, aggressive carcinomas, often driven by high-grade neuroendocrine components, with a poor prognosis (2). Amphicrine neoplasms contain neuroendocrine and exocrine components in the same cell. Clinical Case: A 34 year-old woman with asthma, hypertension, and depression presented with new onset lower extremity edema, facial hirsutism, mood changes, polyuria and polydipsia. She had an elevated morning serum cortisol of 52 ug/dL (normal < 20) with plasma ACTH 42 pg/mL (normal < 50), 24-hour urine free cortisol of 1003 mcg (normal < 50), K+ of 2.6 mEq/L, and fasting glucose 164 mg/dL. CT showed multiple hepatic lesions, pulmonary nodules, a pancreatic tail lesion, and lymphadenopathy concerning for metastatic disease. Her adrenal glands were thickened bilaterally without nodules. A pituitary MRI was normal. These findings were concerning for ectopic CS. She was admitted due to rapidly developing symptoms. Potassium, insulin, sitagliptin, and prophylactic anticoagulation were started. Spironolactone and ketoconazole were initiated while awaiting biopsy results of liver and pancreas lesions. Osilodrostat was not available and a trial of metyrapone was poorly tolerated. The liver and pancreatic tail lesion biopsy revealed metastatic MiNEN with amphicrine features, of pancreatic origin, with Ki67 proliferation index of 70%. Section staining of pancreas and liver biopsies were negative for ACTH. A Ga-68 Dotatate scan showed minimal uptake, so octreotide was not prescribed. Palliative chemotherapy was planned. Although ketoconazole was titrated to 1600 mg/day, urine free cortisol levels and serum free cortisol levels did not reach target. Cushing disease was considered but not suspected, as ACTH levels remained modest despite a relative decrease in cortisol level. Given significant morbidity from uncontrolled hypercortisolism, and plans for urgent initiation of systemic chemotherapy, after multidisciplinary discussion the patient was treated with a surgical bilateral adrenalectomy. Post-operative morning serum cortisol measured 8.3 ug/dL. After one week, palliative chemotherapy with FOLFIRINOX (oxaliplatin, leucovorin, fluorouracil, and irinotecan) was initiated. She was discharged home on stress dose steroids with plan for taper. Conclusion: Ectopic ACTH secretion is a rare phenomenon, particularly when presenting with a rare case of metastatic pancreatic MiNEN with amphicrine features, associated with significant morbidity. To improve tolerance and survival of further treatment, early surgical bilateral adrenalectomy should be considered. References: 1. Young J et al. Eur J Endocrinol 2020. 2. Frizziero M et al. J Clin Med 2020. Presentation: 6/3/2024