Pathological features of intestinal T-cell lymphoma in Shiba dogs in Japan

Intestinal T-cell lymphoma is being more frequently diagnosed in dogs owing to the wide availability of endoscopy and clonality analysis in veterinary medicine. However, no epidemiological study on intestinal T-cell lymphoma has been previously performed, and hence, information about dog breed, age and sex distributions of intestinal T-cell lymphoma has largely remained unclear. In this study, breed predisposition to canine intestinal T-cell lymphoma was determined by calculating odds ratios and 95% confidential intervals. Of the 43 breeds identified, 7 appeared to have an increased risk of developing intestinal T-cell lymphoma, including Shiba dogs, German shepherds, Cairn terriers, Boston terriers, Papillons, Pugs and Maltese. Immunohistochemistry of representative Shiba cases revealed ubiquitous cytotoxic immunophenotype in both large and small cell lymphomas. Interestingly, CD20 co-expression was observed in 11% of cases. It could potentially be aberrant expression of CD20 or neoplastic transformation of a normal subset of CD20-positive T-cells. A comparison of mean age between representative breeds revealed that Shiba dogs were slightly younger than Miniature Dachshunds (P < .05). However, there was no difference in survival between the 2 breeds. As Shiba dogs are predisposed to chronic enteropathy, there may be underlying inflammatory process contributing to lymphomagenesis of intestinal T-cell lymphoma in this breed. Our findings provide insights into the underlying pathogenesis of breed-specific canine intestinal T-cell lymphoma.