SUN-486 - Aldosterone- and cortisol-co-secreting adrenocortical carcinoma presenting as primary aldosteronism with favorable outcome

Primary aldosteronism (PA) is most commonly caused by aldosterone-producing adenomas, whereas adrenocortical carcinoma (ACC) is a rare etiology. Aldosterone-producing ACC is uncommon and generally associated with aggressive behavior. Cases with concurrent cortisol secretion are even rarer, and their clinical course remains poorly characterized. We report a 55-year-old male who initially presented to the nephrology clinic with hypertension and severe hypokalemia (2.0 mmol/L), where a right adrenal incidentaloma was identified, and he was subsequently referred to the endocrinology clinic. Biochemical testing showed a markedly elevated aldosterone-to-renin ratio (199.4), with serum aldosterone of 63.8 ng/dL and suppressed plasma renin activity (0.32 ng/mL/hr). Confirmatory saline loading and captopril challenge tests were also consistent with PA. Serum cortisol after overnight dexamethasone suppression test was 3.72 μg/dL, suggesting mild autonomous cortisol secretion (MACS). Computed tomography demonstrated a 2.9 cm right adrenal mass with unenhanced attenuation of 27 Hounsfield units and high contrast washout (absolute 77%, relative 62%). Because of marked aldosterone excess with severe hypokalemia and imaging findings suggestive of unilateral disease, laparoscopic adrenalectomy was performed without adrenal venous sampling. Postoperatively, blood pressure and biochemical abnormalities improved. However, histopathological examination unexpectedly revealed ACC with a Weiss score of 3, based on high nuclear grade, atypical mitotic figures, and capsular invasion. The Ki-67 index was low (2.2%). The patient has remained recurrence-free for over 3 years and continues to do well, with sustained normalization of potassium, aldosterone, and renin levels without adjuvant therapy or hormone replacement. This case highlights the importance of thorough evaluation of adrenal tumors with attenuation greater than 10 Hounsfield units in patients with primary aldosteronism, particularly when imaging findings are discordant. Further research is needed to better characterize aldosterone- and cortisol-co-secreting adrenocortical carcinomas and their long-term outcomes.

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