CD34⁺, CD41⁺acute megakaryoblastic leukemia in a dog

Abstract

A clinically normal, 5-year-old intact female German Shepherd dog was presented to the local veterinarian to be spayed. Results of a preoperative CBC included mild nonregenerative anemia, severe thrombocytopenia, and 17% unclassified cells. On cytologic examination of aspirates from the dog's enlarged spleen and peripheral lymph nodes, a population of primitive round cells that occasionally resembled megakaryocytes was observed. A bone marrow aspirate specimen was markedly hypercellular with approximately 65% of marrow cells comprising a homogeneous population of immature hematopoietic cells similar to those found in the spleen, lymph nodes, and peripheral blood. Using immunocytochemical stains with canine-specific antibodies, all neoplastic cells strongly expressed cytoplasmic CD41 and 20-70% of the neoplastic cells expressed CD34 weakly to moderately. Rare (<0.5%) neoplastic cells weakly expressed vWF. The cells were negative for all other markers. Based on these results and the morphology of the neoplastic cells, a diagnosis of acute megakaryoblastic leukemia (AMegL) was made. In spite of treatment, results of a CBC performed 1 week later indicated progressive anemia and thrombocytopenia, and the dog was euthanized. To our knowledge, this report documents the first case of canine AMegL diagnosed with both anti-canine CD34 and CD41 antibodies.

Thrombocytosis and central nervous system involvement in a case of canine acute megakaryoblastic leukemia

“…More than 80% of the neoplastic cells were CD61 positive, whether they were multinucleated or not, as previously reported in eight cases of AML‐M7 . The inconsistent vWF positivity in the present case has already been reported in six of the cases of canine AML‐M7 that tested for vWF . In the case described here, only the more differentiated neoplastic cells (multinucleated) were positive for vWF.…”

“…Acute megakaryoblastic leukemia is a rare neoplastic disease of dogs, with only 18 spontaneous cases reported in the literature . Here, we report a case of AML‐M7 that raises the issue of the blast percentage threshold to distinguish MDS from acute myeloid leukemia (AML).…”

“…Thrombocytosis during initial diagnoses is an uncommon feature of canine AML‐M7 (only two cases reported); however, in contrast, thrombocytopenia is fairly common (15 cases reported). This case emphasizes the fact that AML‐M7 should be listed as a differential in cases of canine thrombocytosis.…”

Use of CD9 and CD61 for the characterization of AML‐M7 by flow cytometry in a dog*

“…Poorly differentiated megakaryoblasts may resemble lymphoblasts or myeloblasts based on routinely stained blood or bone marrow smears. To make a specific diagnosis for AML‐M7 immunophenotype technique is required 19 . Immunophenotyping is the most sensitive and specific diagnostic tool for determination of cell origin in poorly differentiated acute leukaemias, making the diagnosis more accurate 20,21 .…”

Myeloperoxidase‐positive acute megakaryoblastic leukemia in a dog

“…Acute megakaryoblastic leukemia is an uncommon form of acute myeloid leukemia (AML) in dogs, and reported cases include experimentally‐induced and spontaneous cases . In 1991 the Animal Leukemia Study Group proposed that the presence of ≥ 30% blast cells in relation to ANC in peripheral blood or bone marrow indicates AML when bone marrow erythroid cells are < 50% of ANC .…”