Cancer of the pancreas.

The malignant growth may originate either in the duct cells or acini of the gland, or in the islets of Langerhans. Cancer of the islet cells is uncommon and is discussed in a later section. About 80% of tumours are adenocarcinomas which arise from ductular epithelium. The neoplasm is hard and scirrhous and the cells are columnar or cuboidal with clear-cut cellular outlines. Cancers arising from the acini account for 13% of growths. These tumours are softer and more bulky. The cells are polygonal or round with indistinct outlines and hyperchromatic nuclei. The site of origin is indeterminate in the remaining growths. It is customary to distinguish between cancers arising from the head, the body, and the tail of the gland. Between 50% and 70% of cancers arise in the head. It is probable that the frequency of cancer in different anatomical subdivisions of the organ is proportional to the amount of tissue in the various parts. The growth may have a multicentric origin. Since the pancreas has no limiting capsule and has a rich venous and lymphatic drainage extrapancreatic extension of the growth is frequently early and widespread. Cancers of the head show early involvement of the bile duct, duodenum, and regional lymphatics. More distal metastases are less common and are usually seen in the liver. Extrapancreatic spread is more striking in cancer of the body and tail, possibly because the diagnosis is usually made at a later stage.