Tumours of the pancreas.

Tumours of the pancreas occur most commonly in dogs and cats and only rarely in other domestic species. The incidence of neoplasms, both exocrine and endocrine, increases with age. Exocrine adenocarcinomas are the most common malignant tumours and have three fairly distinct morphological patterns: small tubular, large tubular, and acinar cell (rare). They readily metastasize, usually before clinical signs are apparent. A "starry sky" pattern with clear histiocytes scattered among tumour cells is a regular feature of poorly differentiated areas of small tubular adenocarcinomas and undifferentiated carcinomas. Islet cell tumours occur in a significant number only in dogs. Metastases are found in about half of the tumours, but malignancy cannot always be predicted by the morphological appearance. Slightly more than half of the islet cell tumours reported in the dog have been associated with clinical signs of hypoglycaemia. Nodular hyperplasia and exocrine adenomas are sometimes difficult to differentiate. Adenomas are considered rare while nodular hyperplasia is common in old animals.