Pancreas - Endocrine pancreas

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Pancreas

Endocrine pancreas

Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 14 December 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Consists of islets of Langerhans, represents 1% of pancreas (percentage higher at birth)
● Round, compact, highly vascularized with scanty connective tissue
● More irregular outline and trabecular arrangement in posterior head of pancreas with cells producing pancreatic polypeptide
● Size of islets usually 0.1 to 0.2 mm, endodermal origin, one million islets present in pancreas
● Islet composition: beta cells (68%), alpha cells (20%), delta cells (10%), PP cells (2%), serotonin cells (rare)
● Post-gastrectomy, may get islet hypertrophy, then beta cell proliferation, then atrophy and amylin deposits (Hum Pathol 2000;31:1368)
● Alpha cells: produce glucagon; peripherally dense and round on EM
● Beta cells: produce insulin and islet cell amyloid polypeptide (amylin), crystalline appearance on EM with surrounding halo
● Delta cells: produce somatostatin (represses release of insulin and glucagon), large pale granules on EM
● D1 cells: produce vasoactive intestinal polypeptide (VIP), which induces glycogenolysis and hyperglycemia, stimulates GI fluid secretion and causes secretory diarrhea
● Enterochromaffin cells: synthesize serotonin, produce carcinoid syndrome
● Gastrin cells: pancreas usually lacks gastrin producing cells, although gastrinomas are common
● PP cells: produce pancreatic polypeptide, which stimulates secretion of gastric and intestinal enzymes and inhibits intestinal motility; present in islets and scattered in exocrine pancreas; more PP cells in posterior head of pancreas (from ventral bud)
● Nesidioblastosis: islets in intimate association with ducts with formation of ductuloinsular complexes
● Nesidiodysplasia: loss of the usual centrilobular concentration of larger islets, with increased small irregularly distributed aggregates of islet cells; also increase in beta cell nuclear size and DNA content; may be associated with endocrine neoplasms (Hum Pathol 1988;19:1215)
● Peliosis: selective congestion and dilation of vessels of islets only, not seen in vessels elsewhere

Micro images
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Islets in newborn: figure A-well lobulated pancreatic tissue with islet (arrows) at periphery of a lobule
figures B/C-insulin and somatostatin immunostains reveal small islet cell clusters as well as well formed islets with central insulin cells and peripheral somatostatin cells

Islets: cells with clear cytoplasm (centroacinar and ductal cells) stand out from a background of basophilic acinar cells

Adult pancreas-ordinary type islet: regular contour and compact shape is characteristic of islets rich in beta cells

Adult pancreas-irregular type islet: irregular contours and trabecular architecture are characteristic of islets rich in PP cells

Adult pancreas: distribution of islet cell types in pancreatic tail

Islet rich in PP cells in posterior part of pancreatic head

Islet hyperplasia of Beckwith-Wiedemann Syndrome: note crowding without fusion of islets inside pancreatic lobules. (Courtesy of Dr. Cesare Bordi)

Nesidioblastosis in adult with persistent adult hyperinsulinemic hypoglycemia: clustering of irregular islets in vicinity of small ductules

Positive stains
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● Chromogranin, synaptophysin, neuron specific enolase, neurofilament

Electron microscopy images
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Zymogen granules

Adult pancreatic islet cells: glucagon cell (bottom), insulin cell (upper right), somatostatin cell (left) are seen. Note the fenestrated capillary vessel at upper left

End of Pancreas > Endocrine pancreas

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