NTHL1 and polyposis: NTHL1 heterozygotes do not appear to be at clinically significant increased risk for polyposis and/or CRC (Elsayed et al., 2020; NCCN Guidelines, 2022) and BC (Kumpula et al., 2020), but a slightly increased risk cannot be excluded (Li et al., 2021), as has been described for patients with heterozygous variants in the MUTYH gene (Win et al., 2014).