MLH1 and neoplasm: The biomarker patterns in MMR-deficient cases were not always coherent with expected mismatch repair biology (i.e. some cases showed MLH1 loss with intact PMS2, or MSH2 loss with intact MSH6) [38, 40], a result that may arise from false negatives from tumor heterogeneity that is not adequately assessed using tissue microarrays [41].