Abstract
In a 6-year-old, uncastrated, mixed-breed dog with a main complaint of repeated diarrhea, masses were found in the abdominal cavity and the intestine by radiography with and without contrast medium, and by ultrasonography. Extramedullary plasmacytoma was suspected by fine needle aspiration. Because of the danger of perforation, the abdomen was opened, and many tumors were found in the liver, spleen, and jejunum, as well as enlarged mesenteric lymph nodes. Remission was obtained by partial resection of the tumors and combination chemotherapy, but the dog died on the 253rd day.