a) focal papillary proliferation of the epithelium of the main pancreatic duct of a hamster. Note the lack of continuity between the hyperplastic foci. In such lesions, generally a few or many endocrine cells are present. H&E × 32. b) Part of a malignant epithelium in a male with pancreatic adenocarcinoma. Note the presence of insulin-positive cells (brown in color) at the base of papillary configuration of the epithelium. Mulilabeling with several antibodies against the four islet hormones reveals a larger number of immunoreactive cells. ABC method, × 120.