In the Non-CNS LS-unrelated tumor group in our study, the proportion of patients with PMS2 (43.4%) was the highest, and this ratio was significantly greater than that in the other two groups; however, the proportion of patients with MLH1 was significantly lower in the Non-CNS LS-unrelated group than in the Non-CNS LS-related group. This evidence concerns the gene MLH1 and neoplasm.