THU013 A Rare Case of Ectopic Cushing’s Syndrome Caused By Metastatic Parotid Gland Carcinoma

Disclosure: E. Punni: None. I. Goyal: None. Introduction: Ectopic Cushing’s Syndrome (ECS) is a rare condition that accounts for only a small percentage of all Cushing’s syndrome cases. Although rare, the typical tumors associated with ECS are small cell lung carcinomas, bronchial carcinoids, pancreatic neuroendocrine tumors, medullary thyroid carcinomas, thymic carcinoids and pheochromocytomas. Metastatic acinic cell carcinoma (ACC) of the parotid gland has very rarely been associated with ectopic Cushing’s syndrome. Case Presentation: A 67-year-old Caucasian male with a known diagnosis of high grade metastatic ACC of the parotid gland presented to the hospital with progressively worsening proximal muscle weakness and bilateral lower extremity edema of 6 weeks duration. A month prior to presentation, he developed persistent hypokalemia requiring potassium supplementation and was diagnosed with new onset type 2 diabetes mellitus. Laboratory results on admission were remarkable for low potassium at 2.5 mEq/L (N: 3.5-5.3 meq/L), a random cortisol level of 107 mcg/dL (N: 6 - 30 mcg/dL), and an ACTH level of 485 pg/mL (N: 7.2 - 63.3 pg/mL). Subsequently, a 24-hour urine cortisol was > 1600 ug/24 hours (N 5-64 ug/24 hours). A 1 mg dexamethasone suppression test failed to suppress an 8 a.m. cortisol with level of 110.8 mcg/dl (N < 1.8 mcg/dl). Following, an 8 mg dexamethasone suppression test also failed to suppress 8 a.m. cortisol with a value of 100.8 mcg/dl. A MRI of the pituitary with and without contrast showed mild diffuse enlargement of the pituitary gland concerning for pituitary hyperplasia. At the time, ECS was highly suspected given the rapid course of patient’s presentation, known metastatic malignancy, and failed 8 mg dexamethasone suppression test. An inferior petrosal sinus sampling (IPSS) could not be performed given the patient’s guarded condition. Instead, a PET/CT Ga-68 DOTA-TATE scan obtained showed widespread DOTA-TATE avid malignancy concerning for neuroendocrine type tumor. Patient was a poor surgical candidate, therefore bilateral adrenalectomy could not be performed for the rapid treatment of ECS. Patient was started on a steroidogenesis inhibitor ketoconazole. However, he elected to undergo hospice care and passed away shortly after. Conclusion: This case is particularly interesting given that metastatic ACC of the parotid gland causing ECS is rare with only a few cases reported in the literature. This case highlights the importance of maintaining a high degree of suspicion for diagnosing ECS especially when patients present with rapid onset of signs and symptoms of Cushing’s syndrome and a known underlying malignancy. Recognizing less common causes of ECS may prompt early diagnosis and intervention. Presentation: Thursday, June 15, 2023