Familial colorectal cancer type X: polyp burden and cancer risk stratification via a family history score

Background: Patients fulfilling Amsterdam-1 criteria without mismatch repair deficiency (termed familial colorectal cancer type X (FCC type X)) were reported to have lower cancer risks than classic Lynch syndrome. This study investigates the polyp and cancer burden of this population and demonstrates relationships with a family history score (FHS). Methods: The Jagelman Registry was queried for patients meeting Amsterdam criteria with microsatellite stable/low colorectal cancers. The risk of colorectal neoplasia was ascertained using a published FHS. Polyp distribution, histology and cumulative counts as well as extra-colonic tumours in the pedigree were reviewed. Results: Twenty-one patients (9 males, 12 females) met study criteria. The median lifetime polyp count was 3 (range 1–36). FHS ≥ 8 (80%) was significantly associated with an increased risk of colorectal cancer compared with those with scores