A 10-year-old female mongrel dog presented with abdominal distension. Physical, radiographic, and ultrasound examinations detected an intestinal mass and ascites. Laparotomy revealed that the mass originated from the cecum and disseminated in the omentum and pancreas. Surgical resection of the mass and disseminated lesions was performed. Histopathological examination revealed the mass and lesions to be gastrointestinal stromal tumors (GISTs). Imatinib mesylate (10 mg/kg/sid) was administered for 355 days postoperatively. The dog survived for > 855 days with no recurrence and metastasis. Adjuvant chemotherapy with imatinib mesylate may be an effective treatment for GIST.

A 13-year-old intact male Shih-Tzu presented with a 2-month history of gastrointestinal signs. A mechanical ileus developed due to an obstruction from an intramural tumor in the small intestine that was surgically resected. The tumor was diagnosed as a high-grade intestinal T-cell lymphoma with incomplete margins and serosal and mesentery extension. CHOP chemotherapy (vincristine, cyclophosphamide, doxorubicin, and prednisolone) was applied, but during the CHOP protocol, the dog developed a nodule on the skin in the scapular area. Histopathological examination of a punch biopsy revealed a high-grade cutaneous T-cell lymphoma. Lomustine was administered and the cutaneous T-cell lymphoma was surgically resected and histologically diagnosed to have complete margins. However, the dog experienced progressive disease. With adjuvant chemotherapy including dexamethasone, melphalan, actinomycin D, and cytosine arabinoside (DMAC), and chlorambucil, methotrexate, and prednisolone (LMP), the patient lived for 571 days in relatively good health condition. No evidence of recurrence nor metastasis was revealed at necropsy. This case suggests the benefit of surgical resection for both intestinal and cutaneous T-cell lymphoma lesions. However, further studies are required to investigate the effect of chemotherapy, remission rate, survival time, and impact on the quality of life.