MSH2 and neoplasm: Heterogeneous expression of the PMS2 protein as well as the protein pair MLH1/PMS2 was observed in two tumors (16.7%), MSH2/MSH6 was observed in seven (58%) tumors (two of which also expressed heterogeneity for MLH1/PMS2) and heterogeneous nuclear expression of the MSH6 protein was observed only in one (8.3%) tumor.