BRAF and colorectal cancer: TGFBR2, BAX, IGF2R, MSH3, MSH6 microsatellite sequences, BRAF and KRAS mutation frequency and MLH1 promoter hypermethylation status in the MSI-H colorectal cancer according to the large bowel of origin (rectal/sigmoid carcinomas compared with those located elsewhere in the colon from both series)