402 Background: Lynch syndrome is a well-described cause of hereditary colon cancer. A point of the Amsterdam II criteria, which defines Lynch syndrome, is to exclude familial adenomatous polyposis (FAP). FAP is caused by mutations in the APC gene and is defined as the presence of 100+ adenomas. The attenuated form of familial adenomatous polyposis (AFAP) can be considered when an individual has 10-99 adenomas. While adenomatous polyps may be a part of the Lynch syndrome phenotype (as a precursor to carcinoma), the assumption is that Lynch syndrome and APC-associated polyposis do not have overlapping phenotypes. Methods: A retrospective analysis was performed on 8,202 individuals with a personal history of adenomatous polyps that had clinical genetic testing for Lynch syndrome (including genes MLH1, MSH2, MSH6, PMS2, and EPCAM) between January 2006 and July 2013. Patient adenoma history was collected on the test request form. The inclusion criterion was limited to personal history of adenomatous polyps and did not depend on personal or family history of cancer. Patients were excluded if the test performed was either targeted mutation testing or single gene testing, presumably based on prior immunohistochemistry tumor testing. Results: Of 8,202 patients with a personal history of adenomatous polyps that underwent Lynch syndrome testing, 610 (7.4%) were positive for a mutation. Mutations were detected in patients with a wide distribution of cumulative adenomas (Table). Seventy-five of the patients with a Lynch syndrome mutation had an adenomatous polyp phenotype suggestive of either FAP (100+ adenomas) or AFAP (10-99 adenomas). Of these 75 patients, 19 underwent APCtesting, all of whom were negative for a mutation. Conclusions: Individuals with an adenoma history, who were tested for Lynch syndrome, had an overall 7.4% mutation positive rate, indicating an overlapping phenotype between Lynch syndrome and FAP/AFAP. This overlap supports consideration of a gene panel test approach. [Table: see text]
Complete Regression of the Adenomatous Polyps in a Patient affected by Familial Adenomatous Polyposis after Prolonged Administration of Phytoestrogens and Sulindac
