Fig. 3

This is a classic example of a conventional pancreatic ductal adenocarcinoma (PDAC) with microsatellite instability, assessed by immunohistochemistry. a An infiltrating PDAC gland is centrally located on the left (arrow), and a normal endocrine islet is on the right (asterisk). Hematoxylin-Eosin staining, original magnification X10. b Loss of expression of the MMR protein MLH1 with immunohistochemistry. The infiltrating PDAC gland is totally negative (loss of protein expression), and the same time the endocrine cells of the islet are positive, as well as lymphocytes, endothelial and stromal cells in the periphery (the expression of the MMR proteins in non-neoplastic cells is used as an internal control demonstrating the reliability of the immunohistochemical analysis). Original magnification X10. c, d Conserved expression of the MMR proteins MSH2 (c) and MSH6 (d). Original magnification X10. e Loss of expression of the MMR protein PMS2 with immunohistochemistry. The infiltrating gland is totally negative (loss of expression), and the same time the endocrine cells of the islet as well as lymphocytes, endothelial and stromal cells in the periphery are positive. Original magnification X10