Primary Solid and Cystic Tumours of the Exocrine Pancreas in Cats.

Tumours of the exocrine pancreas are rare in cats and few cases are described in the literature. Cystic tumours of the pancreas are not included in the World Health Organization (WHO) international histological classification of tumours of domestic animals. The aim of this study was to characterize the pathology of primary epithelial tumours of the feline exocrine pancreas, with emphasis on cystic tumours. We reviewed tumours of the exocrine pancreas in 70 cats, including complete tumours or the entire pancreas (n = 18) and excisional biopsy samples of pancreatic tumours (n = 52). Macroscopically, the tumours were grouped as solid (n = 45) or cystic (n = 25). Solid tumours were subdivided into adenomas (n = 5) and carcinomas (n = 40) and cystic neoplasms into adenomas (n = 15), carcinomas (n = 7) and cases with diverse growth patterns (n = 3). All five grossly solid adenomas had acinar morphology, while the macroscopically solid carcinomas showed acinar (n = 17), tubular (n = 14) or mixed (n = 9) growth microscopically. Cystic adenomas had acinar (n = 2), tubular (n = 12) or mixed (n = 1) growth, while cystic carcinomas had exclusively tubular growth (n = 7). Three cases with cystic lesions showed diverse histopathological growth patterns. The clinical outcome was available in 57 cases. The majority of cats with carcinomas died or were humanely destroyed during or shortly after surgery (n = 32). However, 2/7 animals with cystic carcinomas showed longer survival times. Cats with cystic adenomas had survival times of up to 5 years. The results of this study show that cystic pancreatic tumours should be considered a differential diagnosis in cats with cystic intra-abdominal masses, even though these are not yet described in the WHO classification. Based on the relatively long survival times of cats with cystic adenomas, complete resection with subsequent histopathological examination is recommended.