POLD1 and colorectal cancer: To explore further the possibility of using nuclease P1 for duplex sequencing library preparation from FFPE-derived DNA, we extended our collection of colorectal cancer cases by adding two more MSI-positive cases, three cases with germline biallelic mutations in the MUTYH gene, one case with hereditary POLD1 variant and another one with somatic mutation in POLE gene, as well as four cases with none of these alterations (Table 1).