Based on previous evidence and with the aim of refining the phenotypic characteristics of the NTHL1-associated syndrome, here we evaluated the implication of NTHL1 biallelic mutations in the predisposition to personal or familial history of multiple tumor types, familial/early-onset nonpolyposis CRC, and serrated/hyperplastic polyposis. Here, NTHL1 is linked to colorectal carcinoma.