Clinical, histopathological and immunohistochemical findings in a case of megakaryoblastic leukemia in a dog

The clinical, hematological, and histopathologic features of megakaryoblastic leukemia (M7) were investigated in a 10-year-old female Shih-Tzu dog. Megakaryoblastic leukemia was diagnosed using antihuman platelet glycoprotein (GP IIIa) and anti-human von Willebrand factor (vWF) antibodies. The expression of CD antigen on megakaryoblasts was also assessed using a CD79a monoclonal antibody. Immunological markers allowed visualization of neoplastic megakaryocytes. Antibodies against platelet GP IIIa were demonstrated to be the most useful for the diagnosis of megakaryoblastic leukemia of paraffin-embedded canine tissues. Hematological and histological data coupled with immunohistochemical reactivity for platelet GP IIIa, vWF, and CD79a antigen in blast cells confirmed a diagnosis of M7 megakaryoblastic leukemia.