A case of gastric leiomyosarcoma in a domestic shorthair cat.

Case summary: A 10-year-old male neutered domestic shorthair cat presented with nausea and 1.2 kg weight loss over a 6 month period. Physical examination was unremarkable, and haematological and biochemical results were considered clinically unremarkable. Abdominal ultrasound revealed an 18 mm diameter heterogeneous mass in the stomach at the pyloric sphincter, protruding into the gastric lumen with loss of gastric wall layering. The remainder of the intestinal tract and abdominal viscera were unremarkable and no free fluid was detected. The mass was surgically resected via celiotomy and the adjacent lymph node excised for histopathology. Histopathology of the mass demonstrated neoplastic spindle cell proliferation, which was considered most likely to be of smooth muscle origin, and so a preliminary diagnosis of gastric leiomyosarcoma was given. Complete excision was confirmed. Immunohistochemistry excluded a gastrointestinal stromal cell tumour as a differential and strongly supported the diagnosis of gastric leiomyosarcoma. The cat recovered well postoperatively with supportive treatment. Repeat abdominal ultrasonography 3 and 6 months postoperatively showed no evidence of mass regrowth. Survival time at the time of reporting is 10 months.

Relevance and novel information: To our knowledge, this is the first report of gastric leiomyosarcoma in a cat. Based on this case, gastric leiomyosarcoma should be a differential diagnosis for cats presenting with a gastric mass.