Clinical and immunohistochemical findings of splenic mast cell tumour in a cat: A case report.

A 6-year-old, spayed, female, domestic shorthair cat presented with a 4-month history of chronic intermittent vomiting and anorexia. The haematologic results indicated moderate anaemia and a circulating mast cell population. The abdominal radiography revealed a markedly enlarged spleen. The cytological analysis of the spleen showed a uniform population of mast cells, and a diagnosis of systemic mastocytosis (splenic mast cell tumour with mastocytaemia) was made. This diagnosis was subsequently confirmed by the histopathological examination of the spleen. The immunohistochemistry for KIT showed KIT pattern II (focal cytoplasmic expression). A splenectomy and chemotherapy with vinblastine and prednisolone resulted in remission of the anaemia and other clinical signs. This case report highlights the importance of cytological evaluations of peripheral blood smears and/or aspirates of enlarged spleens for diagnosing splenic mast cell tumours and for quickly initiating the appropriate treatment.