MON-495 Small But Mighty: A Case Of Aldosterone-producing ACC

Abstract Disclosure: T. Schulze Goni: None. N. Genere: None. Background: Adrenal cortical carcinoma (ACC) is diagnosed in about 1 per million individuals annually and is associated with poor prognosis with a 5-year survival rate below 40%. At the time of diagnosis, median tumor size is about 9 cm and 60% have clinically significant hormonal excess, most commonly with hypercortisolemia. Solely aldosterone producing ACC is exceedingly rare. Clinical Case: A 76-year-old woman was admitted for progressive hypertension for 2 weeks and in hypertensive crisis in November 2021. Subsequent evaluation was suspicious for aldosteronism: hypokalemia (2.5 mEq/L), plasma renin <0.6 ng/mL/h, and serum aldosterone 13 ng/dL, with subsequent salt loaded 24-hour urinary aldosterone 102 mcg/24h. Imaging revealed a left 1.5 cm, lipid-poor adrenal adenoma (34 HU). Additional testing included normal 1 mg dexamethasone suppression test (DST), DHEA-S (19.4 mcg/dL) and ACTH (28.3 pg/mL). Adrenal vein sampling localized to the left and the patient proceeded with left adrenalectomy. Surgical pathology showed oncocytic variant of ACC exhibiting positive surgical margins, high-grade Ki-67 proliferation index (40%). Despite adjuvant therapies with adrenal bed radiation, mitotane and hydrocortisone, she developed metastatic ACC with overt Cushing syndrome two years later. Treatment with ketoconazole and osilodrostat provided some improvement but she ultimately passed away due to complications related to the malignancy and cortisol excess. Discussion: This case highlights several important learning points for the care of patients with ACC. First, while ACCs are typically large at diagnosis, smaller tumors can occasionally be malignant. In this case, ACC was not initially suspected, but concern rose due to exquisitely high urine aldosterone. Second, that secretory patterns of ACC can change over time and close clinical and biochemical surveillance is critical in identifying changes in functional status. This patient’s recurrence was confirmed with salivary cortisol, DST and urine steroid profile with new elevations in multiple adrenal metabolites. Although not the standard use for adrenal steroid profiling, we find this to be a useful adjunct for monitoring the course of ACC particularly given its association with high mortality and aggressive behavior. Adrenal steroid profiling can help assess initial hormonal profile of ACC at the time of diagnosis as well as to surveil for recurrent or persistent disease; more studies are needed for best practices of adrenal steroid profiling in monitoring ACC. Conclusion: ACCs can be small at the time of diagnosis. Adrenal steroid profiling serves as an important tool in the management of ACCs by aiding in early detection of recurrence, providing prognostic information, and monitoring treatment response. This is particularly crucial given the aggressive nature and poor prognosis of ACC. Presentation: Monday, July 14, 2025