Diagnosis of acute myeloid leukaemia in a previously diagnosed case of chronic lymphocytic leukaemia in a dog

A 12‐year‐old female spayed Irish wolfhound presented with a 6‐month history of weight loss, chronic vomiting and diarrhoea and a persistent progressive lymphocytosis with previously diagnosed CD8+ T‐cell chronic lymphocytic leukaemia (CLL). CLL was initially diagnosed through flow cytometry of EDTA‐preserved peripheral blood. The decision to treat was based on a progressive circulating neoplastic lymphocytic population in the face of clinical deterioration. Progressive clinical decline was identified in the several weeks after commencement of treatment with chlorambucil and pegylated asparaginase for progressive CLL. Repeated haemogram and blood smear were suggestive of a second morphologically distinct circulating neoplastic population. Repeated flow cytometry of peripheral blood was consistent with a concurrent acute myeloid leukaemia (AML) to previously identified CD8+ CLL. Emergence of AML coincided with development of upwards of five cutaneous lesions, with concern for leukaemia cutis. High‐dose chemotherapy with vincristine (0.7 mg/m 2 ) was commenced. Despite more aggressive treatment, rapid clinical deterioration ensued, and euthanasia was elected. To the author's knowledge, this is the first report of diagnosis of concurrent AML and CLL in a dog.