As shown in Table 1, Sixty-five percent (121 of 186) patients of these HNPCC patients demonstrated loss of at least one MMR protein. The distribution of the loss of MMR gene expression (shown in Table 2) included concordant losses of MLH1/PMS2 staining (82 of 121 patients, 67.8%), MSH2/MSH6 staining (35 of 121 patients, 28.9%) and loss of PMS2 only (4 of 121 patients, 3.3%). This evidence concerns the gene MLH1 and hereditary nonpolyposis colon cancer.