OR02-05 Differences In Genomic Characteristics Of Small Aldosterone-producing Lesions Between Normal And Pathologic Adrenals

Disclosure: J. Lim: None. S. Plaska: None. &. Liu: None. J. Baker: None. A. Blinder: None. W.E. Rainey: None. A.M. Udager: None. Introduction: Primary aldosteronism (PA) – the most common form of secondary hypertension – is characterized by inappropriate adrenal aldosterone production under suppressed renin conditions. The majority of PA is caused by unilateral aldosterone-producing adenomas (APA) and bilateral hyperaldosteronism (BHA). Emerging evidence suggests that BHA is associated with the accumulation of small aldosterone-producing lesions (less than 1 cm in diameter), including aldosterone-producing micronodules (APM) and/or aldosterone-producing nodules (APN). However, previous studies have shown that APM may also be observed in normal adrenals, and thus, the impact of APM and APN on the development and progression of aldosterone overproduction is not well established. In this study, we compare the frequency and distribution of somatic aldosterone-driver mutations in small aldosterone-producing lesions from normal and pathologic adrenals. Methods: Twenty-eight normal adrenals from deceased renal donors (n=24) and patients undergoing radical nephrectomy for renal cell carcinoma (n=4) were compared with 24 pathologic adrenals from patients with PA who underwent adrenalectomy at the University of Michigan. CYP11B2 immunohistochemistry-guided capture was performed to selectively obtain APM and APN DNA from formalin-fixed paraffin embedded tissue, and mutation status for all known aldosterone-driver genes was determined by Ion Torrent-based targeted next-generation sequencing. Results: From normal adrenals, 57 APM from 12 female and 16 male subjects (median age = 49 years) were analyzed, and approximately 46% of these lesions harbored an aldosterone-driver mutation. The most commonly mutated gene in normal samples was CACNA1D (n = 23; 40.4%), but no KCNJ5 mutations were identified, and no significant sex differences were observed. From pathologic adrenals, 56 APM and 7 APN from 17 female and 7 male subjects (median age = 46.5 years) were analyzed, and the frequency of aldosterone-driver mutations (approximately 70%) was significantly higher than normal adrenals (p-value < 0.05). Although CACNA1D mutations were still predominant in pathologic adrenals (n = 33; 52.4%), a number of KCNJ5 mutations were also observed (n = 5; 7.9%) – particularly in APN. Finally, there was a higher rate of aldosterone-driver mutations in small aldosterone-producing lesions in pathologic adrenals from men compared to women (93.3% vs. 62.5%; p-value = 0.051). Conclusions: The frequency and distribution of aldosterone-driver mutations in small aldosterone-producing lesions (APM and APN) in pathologic adrenals are different from those in normal adrenals and may also vary by sex. Further research is needed on how these different APM patterns affect autonomous aldosterone production in patients with PA. Presentation: Thursday, June 15, 2023