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 <8 who are more likely to develop polyps (P < 0.01). Twelve patients (57%) had predominantly left-sided polyps. Ten colorectal cancers (7 left-sided, 3 right-sided) were diagnosed at a median age of 48 (range 30-74) years. Only three tumours were mucinous or demonstrated tumour-infiltrating lymphocytes, typical of high microsatellite instability tumours. All patients had family history of colorectal cancers (CRCs) and at least 10 patients had a family history of uterine or breast cancer. One patient was found to have hyperplastic polyposis syndrome. Conclusions: FCC type X likely represents a heterogenous group of as yet undefined CRC predispositions. The polyp burden and cancer risk are variable and can be somewhat delineated according to an FHS.