MUTYH and neoplasm: In this study, we: (1) evaluate the performance of SBS18 and SBS36 TMSs to identify germline biallelic pathogenic variant carriers and classify variants in the MUTYH gene in a large series of CRCs from the Genetic Epidemiology of Colorectal cancer Consortium (GECCO) tested with custom-designed targeted tumor sequencing assays, and (2) identify somatic mutation associations with biallelic MUTYH carriers within the somatic mutation landscape of CRCs.