Primary gastrointestinal lymphosarcoma with epitheliotropism in three Shar-pei and one boxer dog.

Three male Shar-pei dogs and one female spayed Boxer dog ranging in age from 4 years, 4 months to 7 years, 8 months had 4-7-week histories of diarrhea, progressive anorexia, weight loss, and vomiting. The dogs were depressed, lethargic, and hypoalbuminemic, with losses of 23-39% of body weight. Endoscopic examination revealed gastric ulceration with areas of mucosal hyperemia and pallor. Small nodules with occasional central depressions were present in three dogs. Gastric and proximal duodenal mucosal biopsies showed neoplastic lymphocytes infiltrating the lamina propria, with invasion of the superficial and glandular epithelial basement membrane. Immunohistochemical evaluation of two dogs was negative for anti-canine IgG and positive for anti-CD3. Necropsy of the Boxer and two Shar-peis confirmed epitheliotropic gastric and small intestinal lymphoma in all three dogs, with mesenteric lymph node and hepatic involvement in two and one dog, respectively.