Serial examination of the pancreas from shelter cats euthanized for population control for the prevalence of histologic and immunohistochemical changes

The clinical relevance of pancreatic histologic changes in cats is unclear. Determination of clinical relevance is complicated by the focal to multifocal nature of these lesions, variable clinical presentation of affected cats, and common comorbidities. Examining the histologic changes on serial pancreatic sections from a cohort of young adult shelter cats without externally observable clinical disease could inform what should be considered normal in cats. Pancreata were obtained from 48 cats euthanized for population control. While hypoalbuminemia was common, liver enzyme activity and gastrointestinal panel results were largely unremarkable. The pancreas was sectioned every 1 cm, routinely processed, and evaluated by a board-certified veterinary pathologist. Pancreatic histologic changes were uncommon in this cohort of cats. Hematoxylin and eosin-stained sections that showed lymphocytic infiltrates were recut for CD3 and CD20 immunohistochemistry. The distribution of CD3 and CD20 positive cells and their percentages were recorded. Of 48 cats, 13 cats (27%) had localized lymphocytic infiltrates with a median percentage of affected sections of 14% (range: 7%-92%). There were no differences in observed percentages or distribution of T- or B-cells. Scattered CD3+ T-cells were incidentally identified in intralobular parenchyma. As mild lymphocytic infiltration was uncommon in this group of cats, it may not indicate a physiological response, as the anticipated response to antigenic stimulation would be expected to occur more diffusely and more commonly. Thus, the role of these infiltrates may reflect bystander inflammation or a primary pathological process (pancreatitis) and likely varies depending on the specific disease context.