Distinct Genetic Alterations Drive Cushing Disease Versus Silent Corticotroph Adenomas

Corticotroph adenomas include functioning tumors causing Cushing disease (CD) and silent corticotroph adenomas (SCA), which differ markedly in size, clinical presentation, and aggressiveness. The molecular basis for these differences remains incompletely understood.

To characterize genomic and transcriptomic alterations underlying the divergent clinical behavior of CD and SCA.

Thirty-eight tumors from 34 patients underwent whole-exome sequencing, copy-number variation (CNV) analysis, and mRNA sequencing. Molecular findings were integrated with clinical, radiological, and pathological data.

USP8/USP48 mutations were present in 10 of 21 CD tumors (48%) and were associated with low CNV levels, minimal invasion, and favorable post-operative remission. In contrast, five of 13 SCAs harbored TP53/ATRX/DAXX mutations, all had markedly elevated CNV, and aggressive clinical features. Transcriptomic analysis identified an ATRX-FAM138A mRNA fusion, resulting in loss of ATRX expression in an aggressive tumor. Unsupervised transcriptome analyses defined four clusters. All USP8/USP48-mutant CD clustered together had low CNV and low recurrence rates. Cluster 2 consisted of a mixture of CD and SCA, with intermediate CNV and non-aggressive behavior. Cluster 3 included USP8-wildtype CD with heterogeneous yet generally non-aggressive courses. Cluster 4 represented high-CNV tumors enriched for TP53/ATRX/DAXX alterations, with the highest rates of radiological invasion, persistent disease, and recurrence or progression. Across the cohort, higher CNV was significantly associated with parameters of aggressiveness.

Corticotroph adenomas comprise distinct molecular subtypes. USP8/USP48-mutant CD represents a low-CNV, low-risk group, whereas tumors harboring TP53/ATRX/DAXX mutations exhibit high CNV and aggressive clinical behavior. CNV and mutation profiling may assist in postoperative risk stratification.