B Endocrine islet cell tumours

— arise from pluripotential ductal cells showing neuroendocrine differentiation.

— forming a minority of pancreatic neoplasms (1-5%) usually occurring in adults. Small (<1-2 cm), circumscribed and solid/trabecular/ gyriform/glandular cell patterns with hyaline (±amyloid) stroma. The majority are benign insulinomas (80-90%). Prognosis depends on the functional subtype, adequacy of surgical excision and the extent of disease.

1. Functional hormonal syndrome (60-85%)

gastrinoma: pancreatic head, duodenum, gastric antrum, Zollinger-Ellison syndrome (multiple gastroduodenal ulcers, carcinoid tumourlets or microadenomas). insulinoma: body and tail—psychiatric/neurological symptoms/ hypoglycaemia.

vipoma: body and tail—watery diarrhoea, hypocalcaemia and achlorhydria.

glucagonoma: body and tail—diabetes mellitus/skin rash/stomatitis.

2. Non-functional somatostatinoma: also in the duodenum with a glandular pattern and psammoma bodies and must be distinguished from well-differentiated adenocarcinoma. Ppoma.

neurotensinoma.

calcitoninoma.

small cell carcinoma: ± ectopic ACTH secretion, hypercalcaemia.

Cellular density, atypia, necrosis, mitoses (>2-10/10hpfs) and a Ki-67 index >5% give some guide as to malignant potential but they are not reliable. Better indicators are:

— tumour type: insulinoma, 85-90% benign; gastrinoma, 60-85% malignant.

— size (>2-3cm), site (e.g. duodenal) and invasion of vessels.

— unequivocal evidence of malignancy is gross invasion of adjacent organs, metastases to regional nodes, liver and other distant sites. Tumour growth is indolent and even patients with metastases can survive several years. Some respond to chemotherapy, e.g. streptozotocin. Occasional cases are of poorly differentiated high-grade small cell type.

Association with multiple endocrine neoplasia (MEN) syndrome. The pancreas is involved in 80-100% of type 1 MEN syndrome, gastrinoma being the commonest (50%) lesion. Associated abnormalities are hyper-plasia or tumours of parathyroid, pituitary and adrenal glands.

(c) Mixed exocrine/endocrine carcinoma

— <1%; bivalent amphicrine cells or adjacent foci of mixed differentiation (the endocrine component being at least one-third of the tumour).

(d) Metastatic carcinoma

— direct spread: stomach, colorectum, biliary tract, abdominal mesothe-lioma/lymphoma.

— distant spread: pleomorphic carcinoma of the pancreas has to be distinguished from metastatic malignant melanoma, sarcoma, chorio-carcinoma and large cell lung carcinoma. Small cell lung carcinoma and renal carcinoma.

It can be difficult to distinguish adenocarcinoma of the pancreas and adenocarcinoma of the terminal common bile duct from adenocarci-noma of the ampulla of Vater, as they can share similar histological features of biliary phenotype. Careful examination of the exact anatomical location is required and circumstantial evidence for a point of origin, e.g. an adenomatous lesion in the ampullary mucosa or dysplasia in the pancreatic/bile duct epithelium. Ampullary cancers tend to an intestinal phe-notype and immunoprofile (CK7 negative/CK20 positive) and pancreatic cancers a ductal appearance and different immunoexpression (CK7 pos-itive/CK20 positive). Sometimes the only conclusion can be adenocarci-noma of the pancreatico-ampullary-biliary region.

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