Of note, all adenomas and CRCs were MMR-proficient by immunohistochemistry except for two biallelic MUTYH cases; Pat_301 (2xCRCs at 50 years, one MMR-proficient and one MMR-deficient with MLH1/PMS2 loss), and Pat_315 (1xCRC at 39 years with MSH2/MSH6 loss). Here, MSH6 is linked to adenoma.