Importance of necroscopic examination in the diagnosis of gastric leiomyosarcoma in a dog with sudden death: a case report

Gastric neoplasms are uncommon in dogs and represent less than 1% of all tumors diagnosed in this species. In a survey of gastrointestinal tumors in dogs, it was found that 90% of malignant neoplasms occur in the stomach and epithelial tumors were more frequent than those of mesenchymal origin. The diagnosis of gastric neoplasms is difficult and often occurs late, making the prognosis unfavorable. In mesenchymal tumors of the gastrointestinal tract, immunohistochemical analysis is essential. This study aimed to report a case of gastric leiomyosarcoma in a dog with sudden death. The animal was referred for necropsy at the Veterinary Pathology Service of Faculdade de Ciências Agrárias e Veterinária of Universidade Estadual Paulista “Júlio de Mesquita Filho” (FCAV – UNESP) and two nodules were observed in the cardia, each 2.0 cm in diameter, whitish, rounded, and firm. The stomach presented a bloody food bolus, and the fecal content was blackened throughout the intestinal extension. The cause of death was a hypovolemic shock. On histopathological examination, the mass corresponded to a proliferation of mesenchymal cells with mild atypia, the diagnosis of which was suggestive of gastric leiomyosarcoma. A gastrointestinal stromal tumor (GIST) is the principal differential diagnosis, so histological sections of the gastric nodules were subjected to immunohistochemical (IHC) analysis. The neoplastic cells were positive for S100, 1A4, Desmin, and HHF35 and did not express DOG1, ruling out the origin of GIST tumor cells. The present report demonstrates the importance of necroscopic examination to conclude the cause of death and the immunohistochemical technique to confirm the diagnosis of mesenchymal neoplasms.