MLH1 and colon adenocarcinoma: used laser microdissection and NGS techniques to analyze the challenges to the interpretation of IHC results and MSI assessment posed by heterogeneous MMR-protein expression; they found that in one case of a colon adenocarcinoma with heterogeneously expressed MLH1 and PMS2, the MLH1/PMS2 expression-preserved region had MSS and the MLH1/PMS2 expression-lost region had high MSI.