FRI137 Histologic And Genetic Characteristics Of Primary Aldosteronism In Late Adulthood

Disclosure: A. Blinder: None. K. Nanba: None. D. Sapiro: None. J. Baker: None. C. Liu: None. I. Bancos: None. M. Lyden: None. W. Young: None. H. Wachtel: None. D. Cohen: None. J. Luther: None. T.A. Williams: None. M. Reincke: None. T. Else: None. T.J. Giordano: None. A. Udager: None. W.E. Rainey: None. Background: There is accumulating evidence that changes in adrenal histology and regulation of renin-angiotensin-aldosterone system occur with age. Primary aldosteronism (PA) is the most common cause of endocrine hypertension. Recent clinical studies suggest unique characteristics of PA in elderly patients, including high prevalence of comorbidities and low clinical cure rate after adrenalectomy. However, histologic and genetic features of PA in late adulthood have not been well elucidated. Objective: To determine histologic and genetic characteristics of PA in late adulthood. Methods: Seventy-six patients who underwent unilateral adrenalectomy at the age of 60 or older were included in this study. Formalin-fixed, paraffin-embedded (FFPE) sections of resected adrenal tissue were used for the analysis. Aldosterone synthase (CYP11B2) immunohistochemistry (IHC) was performed to identify the source of inappropriate aldosterone production. Histologic classification was made according to the HISTALDO (histopathology of primary aldosteronism) consensus. CYP11B2 IHC-guided DNA capture followed by sequencing analysis using direct Sanger sequencing or ion torrent based next-generation sequencing (NGS) was performed. Results: Median age of the studied patients was 70 (interquartile range: 64-73). Based on the CYP11B2 IHC, histologic diagnosis was made as follows; aldosterone-producing adenoma (APA, n=23), aldosterone-producing nodule (APN, n=41), and non-functioning adrenocortical adenoma (NFA, n=6). The remaining six cases had multiple CYP11B2-expressing neoplastic lesions, including APA with APN (n=2) and multiple APNs (n=4). Co-existence of NFA with APA or APN(s) was also observed in 13. Sequencing analysis revealed that somatic KCNJ5 mutation was the most frequent genetic alteration in APA (7/23, 30%), whereas somatic CACNA1D mutation was the most common genetic cause of APN (20/39 with successful sequencing, 51%). Of the 18 sequenced NFA DNA samples, two had somatic mutations in CTNNB1 (n=1) and GNAS (n=1). Conclusion: APN is the major histologic feature of PA in late adulthood. Co-existence of NFA also appears to be a frequent observation in this age population. Somatic CACNA1D and KCNJ5 mutations are common in APN and APA, respectively. Presentation: Friday, June 16, 2023