Acute myeloblastic leukaemia in a dog.

Morphological and cytochemical characteristics of both bone marrow and peripheral blood cells as well as an appreciation of the course of the disease, were found to be important in making the correct diagnosis in a dog with acute myeloblastic leukaemia similar to the M-2 type (FAB classification) of man. Busulfan treatment resulted in only a limited effect, mainly consisting in a reduction of the number of nucleated cells in the peripheral blood. Even under busulfan treatment, however, the relative blast count in marrow and peripheral blood increased, indicating that most blast cells were not susceptible to the action of busulfan. The total survival time of the dog was 94 days, including 24 days from hospitalization and diagnosis until euthanasia in a moribund state. Based on the assessment of morphological abnormalities in leukaemic cells and of mitotic indices in bone marrow smears, it is tentatively concluded that the acute myeloblastic leukaemia in this dog arose in the pluripotent haematopoietic stem cell compartment giving rise to the formation of erythrocytes, eosinophils, neutrophils and monocytes as well as megakaryocytes and that the proliferation rate of cells of the myeloblastic clone was decreased, although an increase in the size of the potentially dividing compartment might have occurred.