MSH6 and neoplasm: In some tumor types, the immunohistochemical evaluation (IHC) of PD-L1 and/or mismatch repair system proteins (MMR) (MSH2, MSH6, MLH1, and PMS2) expression is recommended to allow ICI administration, which can favor the anti-tumor immune response; combined MMR/PD-L1 testing was rarely performed in PA [21,22,23,24,25,26,27,28,29,30,31,32,33,34].