Leukemia cutis as a prominent clinical sign in a dog with acute myeloid leukemia.

An eight-year-old male neutered crossbreed dog presented with erosive and ulcerative cutaneous lesions in the inguinal regions, the medial aspect of both thighs, and the stifles. Hematologic assessment revealed nonregenerative anemia, thrombocytopenia, and high numbers of neoplastic mononuclear cells with a variable degree of maturation. The mononuclear neoplastic cells, with nuclei measuring 10-20 microns in diameter, accounted for 57% of the nucleated blood cells. In addition, the blood contained increased numbers of mature neutrophils and monocytes with atypical morphology. Cytologic examination of the right popliteal lymph node found high numbers of large mononuclear cells with similar morphology to those in the peripheral blood. Flow cytometry of peripheral blood revealed expression by the mononuclear neoplastic cells of the pan-leukocyte marker CD45 and myeloid markers CD14, MAC387, and myeloperoxidase (MPO). These results confirmed a diagnosis of acute myeloid leukemia (AML). Computed tomography found moderate nodular hepatosplenomegaly and multifocal bi-cavitary lymphadenopathy. Histopathologic examination of biopsies from the cutaneous lesions identified infiltration of the dermis by intermediate to large neoplastic round cells. Further treatment was declined, and the owners elected euthanasia. Postmortem examination confirmed AML involvement in the bone marrow, peripheral and intracavitary lymph nodes, heart, liver, kidney, and skin. Neoplastic cells in the bone marrow and skin showed positive immunolabeling for ionized calcium-binding adaptor protein 1 and MPO. To the best of our knowledge, this is the first report of ulcerative cutaneous lesions observed among the presenting clinical signs in a dog with AML and secondary leukemia cutis.