Formation of malignant ductular structures within hamster's islets. a) The lesions is confined to the islets and is sharply demarcated from the surrounding tissue by a layer of fibrosis and inflammatory cells invaded by cancer. H&E × 30. b) Similar lesions showing irregularly shaped malignant glands replacing the islet. H&E × 30. c) In this lesions most part of islet is replaced by malignant gland and sclerosis. Note the sharp delineation of the lesions. Local cancer invasion is seen in the lower portion. H&E × 30. d) An atrophic islet in a patients with chronic pancreatitis. A ductular structure (arrow) is composed of light eosinophilc and clear cells intermingled with islet cells. H&E × 120. e) Another atrophic human islet far remote of a cancer. A dysplastic ductular structure (arrow) in the islet without any signs of depression in the surrounding islet cells. H&E × 120. f) An islet in the vicinity of a well-differentiated adenocarcinoma containing large atypical cells (arrows) intermingled with intact islet cells. H&E × 72. g) A human islet cell in a patient with pancreatic adenocarcinoma loaded with material immunoreactive with anti-MUC-1 antibody (fine granules). Although in these islets the immunoreactivity with anti-insulin has diminished, some granules show reactivity with anti-insulin (arrows). × 104,000, h) Normal human islet. One endocrine cell shows a typical cilia identical to those present in ductal-ductular cells. × 7,200. i) Fine structure of a well-differentiated adenocarcinoma, some cells of which show a few regular or rudimentary granules of endocrine type (arrow). × 7,200.