Splenic mast cell tumour in a cat

A blood sample was submitted for routine haematology from a 7-year-old female DSH with a history of marked splenomegaly. A fine needle aspirate of the enlarged spleen was performed and subsequently, the spleen was removed and submitted for histopathology.

Fig 1. Blood smear: there are rare, well-granulated mast cells in the feather-edge (arrow).
Fig 2. A fine needle aspirate from the spleen reveals large numbers of well-granulated and moderately pleomorphic mast cells.
Fig 3. An H&E section taken from the diffusely enlarged spleen similarly reveals effacement of the splenic tissue by densely-packed sheets of mast cells. Granulation is not as obvious in this section compared to the cytology.

Final Diagnosis

Splenic mast cell tumour associated with mastocytaemia (systemic mastocytosis)


Unlike in dogs, circulating mast cells in cats are not typically associated with non-neoplastic disease and their presence should raise the suspicion of so-called visceral/systemic mastocytosis or a mast cell tumour, particularly splenic. The mastocytaemia in this cat persisted following splenectomy.