This difference in penetrance in carrier individuals, if replicated in larger studies, could be sufficient to justify stratifying just individuals with a family history into high-risk groups currently eligible for specialist clinical care (e.g., NICE guidance on familial breast cancer requires ≥30% lifetime risk to be eligible for referral to a specialist genetic clinic in the UK, whilst all Lynch syndrome patients are suggested to have 2 yearly colonoscopy from age 25 for MLH1/MSH2 carriers and age 35 for MSH6 carriers).30 This evidence concerns the gene MLH1 and breast cancer.