Glucagon immunohistochemistry in pancreas in DM after incretin therapy. A–E: Sections of pancreas from DM-I donors (cases 6185, 6186, 6206, and 6203 with sitagliptin) immunostained for glucagon (pink)
with hematoxylin counterstain. Exuberant expansion of glucagon immunoreactive cells is seen as enlarged eccentrically shaped
islets as well as nodular and linear aggregates of cells intimately associated with ducts and demonstrating variable extension
into duct lumens (arrow). C–E: Higher-power images show glucagon immunoreactivity in cells lining ducts. F–I: Pancreas sections from DM-I donors (case 6199, sitagliptin; 6189, exenatide) show immunofluorescent costaining for cytokeratin
(green), glucagon (red), and DAPI nuclear counterstain (blue). Glucagon-expressing cells are present within and adjacent to
keratin-positive duct structures. G: One cell costaining for cytokeratin and glucagon is indicated by the arrow.