MLH1 and neoplasm: Both MSI and MLH1 promoter methylation were significantly more frequent in proximal tumours (MSI in 21 of 43 proximal tumours but only in 4 of 60 distal tumours, P = <0.0001; MLH1 methylation in 13 of 30 proximal tumours but in none of 60 distal tumours, P = <0.0001, Table 1).