THU518 Ectopic Cushing Syndrome In A Case Of Ewing Sarcoma

Disclosure: M. Fasen: None. S.E. Mayson: None. Background: Ewing sarcoma (ES) is a rare and aggressive neoplasm occurring in bone and soft tissue in children to young adults. It is part of a spectrum of neoplastic diseases known as the ES family of tumors that display varying degrees of neuroendocrine features. Ectopic Cushing’s syndrome (ECS) is also a rare but severe condition associated with unregulated ACTH or CRH secretion by neuroendocrine tumors (NETs) that can cause severe hypercortisolism. The most common tumors associated with ECS include small cell lung carcinoma, bronchial carcinoid and medullary carcinoma of the thyroid gland. Sarcomas causing ECS are extremely rare with only a handful of cases reported in the literature, mostly in children. Herein we detail what we believe to be the first reported case of ECS occurring in an adult male patient with ES. Clinical Case: A 23-year-old man with ES metastatic to pancreas, liver and bone was admitted to the hospital with acute on chronic back pain and lower extremity weakness, and subsequently diagnosed with cord compression and neutropenia from chemotherapy. New onset hypertension and refractory hypokalemia were observed prompting endocrinology consultation. Physical examination revealed facial fullness, central obesity and wide violaceous striae on his abdomen and axillae. Biochemical evaluation demonstrated blood glucose consistently over 300 mg/dL, serum potassium 2.5 mmol/L, renin 0.9 ng/ml/hr (0.2-1.6 ng/ml/hr), aldosterone renin ratio < 3.3, morning cortisol 73 ug/dL (4-22 ug/dL), and ACTH 1020 pg/mL (72-63 pg/mL). A 1 mg overnight dexamethasone suppression test yielded a serum cortisol of 90 ug/dL and 24-hour urine free cortisol was 6388 ug/d (<60 ug/d). MRI brain demonstrated a normal pituitary gland, and FDG PET-CT showed new areas of uptake in bone concerning for metastatic progression and new bilateral adrenal enlargement without nodularity. High dose dexamethasone suppression testing was deferred in the context of rapid neuropsychiatric deterioration characterized by somnolence and psychosis. The decision was made to treat immediately with spironolactone and ketoconazole, as well as insulin for hyperglycemia management. His mental status, blood pressure, serum potassium, glucose and cortisol improved following the initiation and titration of medical therapy. He was discharged home with addition of metyrapone and hospice support. Two months later the patient succumbed to his illness. Conclusion: The severity of hypercortisolism is a negative predictor of survival and prompt control should be the main therapeutic goal along with prevention of cortisol-induced complications in patients with ECS. ACTH and CRH immunostaining of the patient’s ES histopathology slides is pending. Presentation: Thursday, June 15, 2023