Chen W, Pearlman R, Hampel H, et al. - Researchers intended to assume MSH6 staining heterogeneity in colorectal cancer by comparative sequencing of different tumor areas for mismatch repair protein (MMR) and DNA polymerase mutations. They examined whole-section slides of 1,754 colorectal cancers for heterogeneous MSH6 staining, defined as discrete tumor areas with the abrupt loss of staining juxtaposed to tumor areas with retained staining. They suggest notifying MSH6 heterogeneous pattern as MSH6 staining is present with a comment stating that the heterogeneous pattern typically does not show germline mutation in MSH6 but is commonly correlated with an abnormality in another MMR gene such as MLH1 or PMS2, or even other DNA repair genes such as DNA polymerase.