Mast cell leukaemia in a mixed breed dog

A 10‐year‐old, spayed, female, mixed breed dog was found to have persistent, severe mastocytemia, with 16%–20% mast cells in the peripheral blood. At presentation, the dog had no cutaneous tumours and no history of previously removed mast cell tumours. Subsequent evaluation revealed neoplastic mast cell infiltration in the spleen, liver and bone marrow. Based on these findings, a diagnosis of mast cell leukaemia was made. Vinblastine chemotherapy was initiated but was discontinued after a single dose due to poor response and progression of clinical signs. This case demonstrates the potential significance of mast cells in the peripheral blood of dogs and emphasises the importance of blood smear evaluation when performing a complete blood count.