Clinicopathological and Endoscopic Features of Diffuse Alimentary Lymphoma in 18 Dogs.

Diffuse alimentary lymphoma (AL) in dogs is an under-characterized entity lacking well-defined diagnostic criteria. This retrospective study evaluated the clinical, endoscopic, histopathological, and immunohistochemical features of 18 dogs diagnosed with diffuse AL between 2017 and 2024. The inclusion criteria for dogs were an abdominal ultrasound, gastrointestinal endoscopy with multiple mucosal biopsies, and the availability of both histopathological as well as immunohistochemical data. Dogs with an intestinal mass were excluded. The duodenum was the most frequently affected segment, with a "cobblestone" endoscopic appearance noted in 53% (9/17) of dogs undergoing upper gastrointestinal endoscopy. Compared to dogs without this feature, those with a "cobblestone" appearance of the duodenal mucosa had significantly lower plasma albumin concentrations (mean: 18.8 g/L, SD: 4.32, range: 19-31 vs. mean: 25.3 g/L, SD: 4.3, range: 19-31; = 0.007), higher CCECAI scores (mean: 11.1, SD: 1.45, range: 9-13 vs. mean: 8.0, SD: 2.27, range: 5-12; = 0.004), and shorter survival time (median: 9 days, range: 4-58 vs. median: 92 days, range: 12-350; log-rank test: = 0.02). While certain endoscopic features-such as a "cobblestone" duodenal mucosal appearance-were associated with more severe clinical and biological profiles, the diagnostic value of these lesions remains to be clarified.