Myeloperoxidase-Positive Acute Megakaryoblastic Leukemia

Abstract

Acute megakaryoblastic leukemia (FABM7) is an unusual but well recognized form of acute myelogenous leukemia in which the bone marrow blast cells are phenotypically recognized by the demonstration of cytoplasmic platelet peroxidase or surface staining for the IIb/IIIa platelet-specific glycoprotein. Herein, the authors report a case of acute megakaryoblastic leukemia that satisfies the accepted French-American-British criteria and in which the blast cells also exhibit evidence of myeloid differentiation, including surface MY7 (CD13) by flow cytometry and immunocytochemical positivity for myeloperoxidase. These findings suggest that megakaryoblasts may be closely related to myelomonoblasts, that they have the potential to partially differentiate along multiple phenotypic lines, and that aberrant phenotypes can occur that do not correspond to known stages of normal maturation. The authors illustrate the difficulty in classification of these aberrant phenotypes by standard cytochemical and morphologic criteria.

Myeloperoxidase‐positive acute megakaryoblastic leukemia in a dog

“…This is an unusual feature of acute megakaryoblastic leukemia in dogs, as in other reported cases imunohisto(cyto)chemical staining for MPO was negative . MPO is a primary granule protein synthesized at the progranulocyte stage of normal granulocytic differentiation and is also found in cells of the monocytic lineage, although in lower concentrations . Co‐expression of GPIIIa and MPO by the leukemic cells in the present case was compatible with concurrent differentiation along megakaryocytic and granulocytic/monocytic pathways, a finding often referred to as “lineage infidelity.” As megakaryoblasts, myeloblasts, and monoblasts arise from a common myeloid precursor, partial differentiation along these 3 pathways is feasible.…”

“…30,31 Co-expression of GPIIIa and MPO by the leukemic cells in the present case was compatible with concurrent differentiation along megakaryocytic and granulocytic/monocytic pathways, a finding often referred to as "lineage infidelity." 31 As megakaryoblasts, myeloblasts, and monoblasts arise from a common myeloid precursor, partial differentiation along these 3 pathways is feasible. This aberrant immunophenotype has been documented in a human case of acute megakaryoblastic leukemia.…”

“…Co‐expression of GPIIIa and MPO by the leukemic cells in the present case was compatible with concurrent differentiation along megakaryocytic and granulocytic/monocytic pathways, a finding often referred to as “lineage infidelity.” As megakaryoblasts, myeloblasts, and monoblasts arise from a common myeloid precursor, partial differentiation along these 3 pathways is feasible. This aberrant immunophenotype has been documented in a human case of acute megakaryoblastic leukemia . Findings suggestive of concurrent granulocytic/monocytic differentiation in acute megakaryoblastic leukemia in dogs have been described in one case in which the neoplastic cells were Sudanophilic and in 3 other cases in which the neoplastic cells stained positively for chloroacetate esterase (CAE) .…”

“…This aberrant immunophenotype has been documented in a human case of acute megakaryoblastic leukemia. 31 Findings suggestive of concurrent granulocytic/monocytic differentiation in acute megakaryoblastic leukemia in dogs have been described in one case in which the neoplastic cells were Sudanophilic 12 and in 3 other cases in which the neoplastic cells stained positively for chloroacetate esterase (CAE). 11,15 In the present case, positivity of the neoplastic cells for CAE may have helped confirm a phenotype consistent with cells of the granulocytic and megakaryocytic cell lineages, as CAE is present in granulocytes and megakaryocytes but not monocytes 30 ; however, CAE staining was deemed unnecessary as lineage infidelity was already demonstrated.…”

U.S.-Canadian consensus recommendations on the immunophenotypic analysis of hematologic neoplasia by flow cytometry: Data analysis and interpretation

“…Megakaryocytic Leukemia (53,74,87) is best recognized by bright expression of platelet glycoproteins CD61 and/or CD41 in a leukemia with relatively little complexity by light scatter. Myeloid antigens CD33 and CD13 are variably expressed, as is CD34, and CD45 can vary from completely negative to brightly positive.…”