Xanthogranulomatous inflammation of the small bowel in a dog.

A case of xanthogranulomatous inflammation of the small bowel in a 12-year-old male American Staffordshire Terrier is described. Disseminated yellow-white nodules 2 to 3 mm in diameter bulging on the serosal surface of the small bowel, as well as on mesenteric tissue, were detected. Histopathologic examination revealed a nodular collection of foamy cells, mainly involving serosal and muscular layers, associated with necrotic areas, hemorrhages, neovascularization, variable numbers of reactive spindle cells, neutrophils, lymphocytes, plasma cells, and rare multinucleated giant cells. Transmural lymphangectasia and mucosal lymphoplasmacytic inflammation were also observed. Both Oil Red O stain and ultrastructural study revealed lipid droplets in the cytoplasm of foamy cells. Lysozyme immunoreactivity was detected in single as well as in clustered foamy cells, while smooth muscle actin was positive in spindle cells and scattered foamy elements. Lymphangectasia associated with lymphoplasmacytic enteritis suggests a component of lymphatic fluid stasis in the pathogenesis of such lesions.