Targeted Mutational Analysis of Cortisol-Producing Adenomas.

BACKGROUND Somatic gene mutations have been identified in only about half of cortisol-producing adenomas (CPA). Affected genes include PRKACA, GNAS, PRKAR1A, and CTNNB1. OBJECTIVE To expand our understanding of the prevalence of somatic mutations in CPA from patients with overt Cushing syndrome (OCS) and "subclinical" mild autonomous cortisol excess (MACE), with an immunohistochemistry (IHC)‒guided targeted amplicon sequencing approach using formalin-fixed paraffin-embedded (FFPE) tissue. METHOD We analyzed FFPE adrenal tissue from 77 patients (n=12 men, 65 women) with either OCS (n=32) or MACE (n=45). Using IHC for 17α-hydroxylase/17,20-lyase (CYP17A1) and 3β-hydroxysteroid dehydrogenase (HSD3B2), we identified 78 CPA (32 OCS-CPA and 46 MACE-CPA). Genomic DNA was isolated from the FFPE CPA and subjected to targeted amplicon sequencing for identification of somatic mutations. RESULTS Somatic mutations were identified in 71.8% (56/78) of the CPA. While PRKACA was the most frequently mutated gene in OCS-CPA (14/32, 43.8%), somatic genetic aberrations in CTNNB1 occurred in 56.5% (26/46) of the MACE-CPA. Most GNAS mutations were observed in MACE-CPA (5/7,71.4%). No mutations were observed in PRKAR1A. In addition to the known mutations, we identified one previously unreported mutation in PRKACA. Two patients with MACE harbored two adjacent tumors within the same adrenal gland: one patient had two CPA, and the other patient had a CPA and an aldosterone-producing adenoma (identified by IHC for aldosterone synthase). CONCLUSION Comprehensive FFPE IHC-guided gene-targeted sequencing approach identified somatic mutations in 71.8% of the CPA. OCS-CPA demonstrated a distinct mutation profile compared to MACE-CPA.