Criteria for the Diagnosis of Acute Leukemia of Megakaryocyte Lineage (M7)

Abstract

For the diagnosis of M7, the bone marrow aspirate shows a leukemic cell infiltrate that comprises 30% or more of all cells. These cells are identified as being of megakaryocyte lineage by the platelet peroxidase reaction on electron microscopy or by tests with monoclonal or polyclonal platelet-specific antibodies. Myelofibrosis or increased bone marrow reticulin are a prominent aspect in most patients with M7. In patients with increased reticulin, the bone marrow sample may be difficult to obtain and the counts done on the marrow films may be misleading. In these patients, the diagnosis of M7 should be based on excellent bone marrow biopsy sections that show an excess of blasts and, at times, increased numbers of maturing megakaryocytes; and on the presence of unequivocal megakaryoblasts in the peripheral blood or bone marrow (or both) as shown by immunologic techniques.

Acute panmyelosis with myelofibrosis: an entity distinct from acute megakaryoblastic leukemia

“…A predominance of megakaryoblasts, identified by their flow cytometric characteristics and/or by their immunohistochemical reactivity with CD42b (Figure 2c), CD31, vWF, or LAT (Figure 2d) was seen in nine of 11 cases. Three AMKL cases (12,15,17) showed a low frequency of CD42b and vWF immunoreactivity but a strong CD31 staining. Case 9 expressed CD42b only and at a low level.…”

“…11 AMKL is diagnosed according to criteria of the WHO system, which closely mirrors those of the earlier FAB classification previously established for this subtype of AML. 12 The main requirement is a minimum of 20% blasts, the majority of which showing megakaryocytic differentiation, usually demonstrated by flow cytometry. 7 Additional morphologic features seen in a variable proportion of cases of AMKL include the presence of abnormal small megakaryocytes with hypolobulated or nonlobulated nuclei and a marked degree of reticulin fibrosis, findings that overlap both APMF and AMKL.…”

Immunophenotyping of acute leukemias and myelodysplastic syndromes

“…In contrast, CD36 is expressed early during erythroid maturation, but it is not specific to erythroid cells, since it is also positive in precursor cells of the monocytic, dendritic, and megakaryocytic lineages (29). Regarding the magakaryocytic lineage, CD61, CD41, and CD42 (which recognize gpIIIa, IIb/IIIa, and IX/Ib, respectively) are considered as excellent markers for the detection of megakaryocytic leukemias (AML M7 FAB subtype) (12,66).…”

“…Since then, immunophenotyping has provided information that contributed to the refinement of already existing morphological classifications of AL and the definition of new prognostic entities among these patients (12)(13)(14). More recently, it has also proven to be of great help for the screening of genetic abnormalities (14 -22), the follow-up of minimal residual disease (MRD) (23)(24)(25), monitoring of patient-specific therapies (26,27), and the study of MDS (28,29).…”

Acute myeloblastic leukemia with minimal myeloid differentiation: phenotypical and ultrastructural characteristics

“…[1][2][3][4] Peripheral blood and bone marrow smears were stained with May-Grü nwaldGiemsa. Cytochemical reactivity against myeloperoxidase (MPO), Sudan Black, naphtol-ASD-acetate with FINa inhibition and alpha-naphtyl acetate was analyzed.…”