SMAD4 and polyposis: The major genes with PVs in patients with colorectal cancer included the MMR genes MLH1, MSH2, PMS2, and MSH6, (accounting for 9% of patients with a PV), followed by APC, TP53, MUTYH, BARD1, ATM, and BRIP1. Patients presenting with polyposis tested positive for PVs in APC (4%), MUTYH (2%), PMS2 (2%), MLH1 (2%), TP53 (2%), and to a lesser extent in PTEN, SMAD4, and ATM. Among patients with gastric and other GI tract cancer, PV’s were found in CDH1, TP53, ATM, MSH2, and PMS2 genes (Table 2).