MLH1 and neoplasm: Immunohistochemically, MLH1, MutS protein homolog (MSH) 2, MSH6 and Postmeiotic segregation increased 2 (PMS2) were all expressed in the nuclei of tumor cells in Cases 2 and 3, whereas MLH1 and PMS2 were not expressed in Case 1, suggesting the mismatch repair function had diminished in Case 1 (Figure 7B, Table 3).