Targeted Molecular Characterization of Aldosterone-Producing Adenomas in White Americans

Context: Somatic mutations have been identified in more than half of aldosterone-producing adenomas (APAs) through mutation hotspot sequencing. The underlying pathogenesis of inappropriate aldosterone synthesis in the remaining population is still unknown. Objective: To investigate the prevalence and spectrum of somatic mutations in APAs using an aldosterone synthase (CYP11B2) immunohistochemistry (IHC). guided next-generation sequencing (NGS) approach. Methods: Formalin-fixed paraffin-embedded adrenal tissue from white American patients with primary aldosteronism who underwent adrenalectomy at the University of Michigan was used. Genomic DNA was isolated from 75 APAs (identified by CYP11B2 IHC). NGS was performed to identify somatic mutations by sequencing the entire coding region of a panel of genes mutated in APAs. Results: Somatic mutations were identified in 66 of 75 APAs (88%). Of the APAs with somatic mutations, six were smaller than coexisting CYP11B2-negative adrenocortical adenomas. The most frequently mutated gene was KCNJ5 (43%), followed by CACNA1D (21%), ATP1A1 (17%), ATP2B3 (4%), and CTNNB1 (3%). In addition to identification of previously reported mutations, we identified five previously unreported mutations (two in KCNJ5, one in ATP1A1, one in ATP2B3, and one in CACNA1D genes). KCNJ5 mutations were more frequent in women (70% vs 24% in men). Conclusion: Comprehensive NGS of CYP11B2-expressing adrenal tumors identified somatic mutations in aldosterone-driving genes in 88% of APAs, a higher rate than in previous studies using conventional approaches.