The term “pancreatic cancer” usually refers to ductal adenocarcinoma. While this entity accounts for 85% of primary pancreatic tumors, a variety of other neoplasms can arise from the range of cell types present in the normal pancreas (ducts, acini and islets) (Table 2.1) . Approximately two-thirds of ductal adenocarcinomas are found in the head of the pancreas. The tumor tends to be very firm and ill-defined (Figure 2.1) Cystic change (usually due to tumor necrosis) can occur but is rare . This is an aggressively infiltrating cancer with a propensity for direct invasion into distal common bile duct, ampulla of Vater, duodenum, blood vessels, nerves and extrapancreatic soft tissue, particularly posterior to the pancreas. Ductal adenocarcinoma is a gland-forming tumor. The glands tend to be round or only slightly angulated, giving the tumor a deceptively indolent appearance (Figure 2.2). There is almost always a dense stromal response to the tumor; this “desmoplastic stroma” of myofibroblasts and collagen can make it difficult to pick out the malignant cells. The glands may be lined by a single layer of cuboidal to columnar epithelium or may show complex papillary growth. Tumor nuclei usually vary in size and shape; in fact, the single most helpful diagnostic finding in a biopsy or cytologic preparation is a 4:1 variation in nuclear size within a single gland (Figure 2.3).
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