Myeloid leukaemia with lymph node invasion in a dog

A 2-year-old German Shepherd Dog presented with acute lethargy, splenomegaly and a mild generalised peripheral lymphadenopathy. On routine haematology, there was a leukocytosis of 31.5 x10*9/L (reference range 6.6-18.4 x10*9/L) and 64% of these cells consisted of large neoplastic round cells similar to those described below in figures 1 & 2.

Fig 1. Aspirate of the prescapular lymph node. 60-70% of the nucleated cells consist of large round immature cells (red arrows) that contain moderate amounts of blue-tan ground glass cytoplasm with small pink-orange granules (azurophilic granulation). These cells are not lymphocytes and are instead typical of myeloid lineage.
Fig 2. Aspirate of the prescapular lymph node. Some of these large immature cells contain indented to band-shaped nuclei (red arrows) suggestive of metamyelocyte differentiation. Mitotic figures are common (black arrow).

Final Diagnosis

Acute myeloblastic leukaemia (AML)


In contrast to acute lymphoblastic leukaemia, myeloblastic leukaemia arises from the myeloid cell line. The neoplastic process may involve the neutrophil, eosinophil or basophil but the neutrophil type is the most common in dogs. Affected dogs often present in good body condition but the course of disease is typically rapid and death usually results from a combination of haemorrhage and sepsis due to myelophthisis with resultant thrombocytopaenia and neutropaenia respectively.