Mismatch repair protein expression immunohistochemical profile (100x). The gastric medullary carcinoma is located at the bottom half of each field, while the overlying unremarkable gastric mucosa is located at the top portion of each field. (a) Loss of MLH1 expression. (b) Loss of PMS2 expression. (c) Intact MSH2 expression. (d) Intact MSH6 expression.