414 Background: The identification of Lynch syndrome carriers is an unmet medical need. Large studies characterizing family history profiles of unaffected individuals diagnosed with Lynch syndrome in the absence of a known family mutation have not been reported. Methods: We queried our laboratory database for unaffected patients who underwent Lynch syndrome genetic testing between September 2010 and May 2013 and had a positive test result. All individuals underwent full sequence and large rearrangement analysis of MLH1 and MSH2, and full sequence analysis of MSH6. Some patients also underwent full sequence and large rearrangement analysis of PMS2 and large rearrangement analysis of MSH6 and EPCAM. Those being tested for a known mutation in the family and patients undergoing single gene testing were excluded. We assessed family history profiles in 200 unaffected patients with genetically confirmed Lynch syndrome. Results: Of the 200 patients, 162 female and 38 male Lynch syndrome carriers were identified. Mutations in MLH1 and MSH2 were the most common (30.0% and 32.5%) while mutations in MSH6, PMS2, and EPCAM accounted for 21.0%, 13.5%, and 3.0% of all deleterious mutations, respectively. Eighteen patients did not have a first or second degree relative with colorectal cancer. Only 37.8% (73/193) of individuals had a first- or second-degree relative meeting the Amsterdam II criteria and 76.8 % (149/194) of individuals had a first or second degree relative meeting the Revised Bethesda criteria. The average PREMM1,2,6 score was 10.0% with 43.5% (87/200) falling below 5%. In this large cohort, 15.5% (31/200) had neither a first or second degree relative who met the Amsterdam II or Revised Bethesda criteria nor a PREMM1,2,6 score of 5% or greater. Conclusions: In order to improve detection of Lynch syndrome in the population, it is important to consider genetic testing in unaffected individuals even in the absence of a known family mutation. Development of guidelines that include having a single affected relative and extra-colonic cancers is needed to support healthcare providers in identifying appropriate patients for testing.
p53, Cyclin-D1, β-catenin, APC and c-myc in Tumor Tissue from Colorectal and Gastric Cancer Patients with Suspected Lynch Syndrome by the Bethesda Criteria
