APC and colorectal carcinoma: Polygenic inheritance has been shown to explain up to ∼15% of the familial CRC risk (Frampton et al., 2016) and at least two cases with CRC and possible digenic and oligogenic inheritance have been reported; these patients had variants in MUTYH and OGG1 (both involved in the base excision repair pathway) and in APC, OGG1, EXO1 and POLQ, respectively (Morak et al., 2011; Ciavarella et al., 2018).