Gastrointestinal stromal tumor associated with hypertrophic osteopathy in a dog

ABSTRACT

Background: Gastrointestinal stromal tumor (GIST) is a malignant mesenchymal neoplasm rarely described in the veterinary routine. The aim of this study was to report a case of GIST accompanied by a periosteal reaction, suggestive ofhypertrophic osteopathy, in a dog.Case An 11-year-old male dog had a history of progressive weight loss, difficulty in locomotion, and dyspnea. During clinical care, increased bone volume was observed. Blood samples were collected for a complete blood count and biochemicalanalysis. The dog also underwent thoracic radiography and abdominal ultrasonography. The test results revealed anemia,leukocytosis, hypocalcemia, hypoalbuminemia, and hypocholesterolemia. The radiographic images of the limbs showeda generalized periosteal reaction, and thoracic radiography indicated changes compatible with mild chronic lung disease.Ultrasonographic findings indicated a neoformation in the intestinal loop of the right mesogastric region and increasedvolume in the left testicle, both of which were indicative of neoplasia. Therefore, the dog was referred for surgery, whereinthe intestinal mass and both testes were removed; the intestinal mass and left testicle were subjected to histopathologicaldiagnosis. The results of the biopsies confirmed that the testicular neoplasm was a seminoma, whereas the intestinal nodulewas compatible with GIST, and immunohistochemical analysis was necessary to confirm the diagnosis. On the basis ofpositive labeling for the antibodies vimentin, desmin, S100, and c-kit, the diagnosis of GIST was confirmed. Therefore,the animal underwent metronomic chemotherapy with 12 mg/m2 cyclophosphamide every 24 h for 3 months, and thereafter every 48 h for 6 months. Moreover, the dog was periodically monitored via imaging (radiography of the anteriorand posterior limbs, abdominal ultrasonography, and computed tomography)...