Aims: To define the occurrence of KRAS and BRAF mutations, microsatellite instability (MSI), and MGMT and hMLH1 methylation and expression in colorectal serrated adenocarcinoma. Methods and results: KRAS codon 12 ⁄ 13 and 59 ⁄ 61 and BRAF V600E mutations, MSI, and MGMT and hMLH1 methylation and expression in 42 serrated adenocarcinomas and 17 serrated adenomas were compared with those in 59 non-serrated colorectal carcinomas (CRCs) and nine adenomas. KRAS and BRAF mutations were observed in 45 % and 33 % of serrated adenocarcinomas and in 27 % and 0 % of nonserrated CRCs (P < 0.001). The KRAS c12G fi A transition was the predominant type of mutation in serrated adenocarcinomas. Forty-two per cent of BRAFmutate
