Diffuse splenomegaly in a cat: splenic mast cell tumour
12-year-old domestic shorthair cat with intermittent vomiting and weight loss. Ultrasound shows diffuse splenomegaly with a mottled hypoechoic parenchyma and no masses elsewhere. Splenic aspirates reveal sheets of well-differentiated mast cells, and the buffy coat smear shows circulating mast cells.
What is the most appropriate treatment?
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A. Palliation only: mastocytaemia indicates terminal disseminated disease
In dogs mastocytaemia carries a worse meaning, but in cats with splenic mast cell tumour it is common and splenectomy still provides a clear benefit.
B. Prednisolone alone, as effective as surgery in the visceral form
Corticosteroids may reduce the mast cell burden somewhat, but they do not match splenectomy, which is the measure that most prolongs survival.
C. Splenectomy with H1 and H2 antihistamines, despite the mastocytaemia
Correct. Mast cell tumour is one of the most common splenic neoplasms in cats, and splenectomy is the treatment of choice: it relieves signs and is associated with survival often exceeding a year. Mastocytaemia is common and does not contraindicate it; protect against degranulation with H1 and H2 blockers.
D. None: it is extramedullary haematopoiesis with normal mast cells
The feline spleen may contain scattered mast cells, but sheets of mast cells with diffuse splenomegaly and circulating mast cells indicate neoplasia.
lightbulb Key takeaway
In a cat with diffuse splenomegaly, aspirate the spleen: mast cell tumour is one of the most common neoplastic causes. Splenectomy is the treatment of choice even with mastocytaemia; treat vomiting with H2 blockers or proton pump inhibitors because of hyperhistaminaemia.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.