Acute myeloblastic leukemia with myelofibrosis (panmielosis with myelofibrosis according to the WHO classification) – diagnosis

Acute myeloblastic leukemia with myelofibrosis (panmielosis with myelofibrosis according to the WHO classification):
• a rare form of acute non-lymphoblastic leukemia (ONLL);
• cytopenia in the peripheral blood, poor uninformative punctate of the bone marrow;

• morphological, cytochemical and immunophenotypic studies of cells are difficult;
• blasts react with MCA to myeloid antigens CD33, CD13, CD117 and MPO. In the presence of erythroid or megakaryocyte antigens, an appropriate subtype of blasts is established;
• in trepanate – hyperplasia and dysplasia of varying severity of individual myeloid shoots, clusters of young elements, including blasts; • the degree of fibrosis varies, in most cases an increase in reticulin fibers is observed;
• the karyotype is usually altered. Complicated chromosomal abnormalities involving chromosome 5 or 7 are most frequent.

Acute megakaryoblastic leukemia (M7 according to FAB classification) – diagnosis

Acute megakaryoblastic leukemia (M7 according to FAB classification):
• makes up 3-5% of all acute non-lymphoblastic leukemias (ONLL);
• in the bone marrow, the progenitors of the megakaryocyte series account for more than 50%;

• blasts are of two types:
1) with irregular outlines and pronounced basophilia of the cytoplasm, moderate nuclear-cytoplasmic ratio;
2) rounded with a high nuclear-cytoplasmic attitude, resembling lymphoblasts in appearance;

• in blasts, moderate activity of α-naphthylacetate esterase, resistant to sodium fluoride, and the absence of butyratesterase, is determined. In some cases, PAS-positive substance is located in the form of large clusters along the edge of the membrane against the background of diffuse staining of the cytoplasm;
• platelet peroxidase is determined by ultrastructural examination in the nuclear membrane and the endoplasmic reticulum of blasts;

• blasts express platelet antigens CD41 (glycoprotein IIb / IIIa) and / or CD61 (glycoprotein IIIa), less often CD42 (glycoprotein Ib), since the latter is expressed in more mature forms. For the diagnosis of M7 ONLL, it is necessary that the number of antigen-positive cells be more than 50%. CD13, CD33, CD36 are also detected;
• A variant of M7 leukemia in children with Down syndrome on the background of a transient myeloproliferative disease is separately highlighted. A number of patients may experience spontaneous remission.

Acute erythromyelosis and erythroid leukemia (M6a and M6b according to the FAB classification) – diagnosis

Acute erythromyelosis and erythroid leukemia (M6a and M6b according to the FAB classification): • accounts for 5-6% of all acute non-lymphoblastic leukemia (ONLL);

1) acute erythromyelosis:

• in the bone marrow, erythroid progenitors account for more than 50% of all cells, myeloblasts, more than 20% of cells of the non-erythroid population;
• cells of the red row have pronounced signs of dysplasia: megaloblastoid changes, dissociation of nuclear maturation and cytoplasm, uneven staining of the cytoplasm, the presence of Jolly bodies, multi-core forms. They increase the number of siderophilic granules, determine the positive PAS-reaction in diffuse and / or granular form;
• erythroid progenitors react with ICA to glycophorin A and hemoglobin A;
• myeloblasts contain granularity, single Auer sticks, are positive in reactions to peroxidase, ASD-chloroacetate esterase and lipids;
• blasts express myeloid lineage antigens CD13, CD33, CD117, and also sometimes CD34 and HLA-DR, react with MCA to peroxidase;

2) erythroid leukemia:

• the blast population prevails in the bone marrow (more than 80%);
• blasts of medium or large size with rounded nuclei, delicate chromatin structure and 1–2 nucleoli, cytoplasm basophilic, without grain, sometimes contains vacuoles;
• blasts do not have myeloperoxidase, lipids, contain granules of PAS-positive substance, nonspecific esterase, acid phosphatase;
• there are no myeloid immunological markers in blasts, early forms express CD36, more mature erythroid glycophorin A antigen;
• Multiple chromosomal rearrangements are detected, often involving chromosomes 5 and 7.

Acute monoblastic leukemia (M5a according to FAB classification) – diagnostics

Acute monoblastic leukemia without maturation (M5a according to FAB classification):
• accounts for 5–8% of all acute non-lymphoblastic leukemias (ONLL);
• blasts of large size, irregular outlines, with moderate or severe cytoplasmic basophilia, with rounded nuclei with 1-2 nucleols; in rare cases, erythrophagocytosis is observed;
• blasts contain a significant amount of nonspecific esterase suppressed by sodium fluoride, a small amount of peroxidase and / or lipids in individual cells;
• blasts express the myeloid antigens CD33, CD13, CD117 and monocytic – CD14, as well as CD4, CDllb, CDllc, CD64, CD36, react with MCA to lysozyme;
• translocations (9; 11), (11; 19), (4; 11) are often detected with the participation of the MLL gene localized at llq23. In accordance with the WHO classification, these observations are categorized as the acute non-lymphoblastic leukemia category with recurring cytogenetic abnormalities.

Acute monoblastic leukemia with maturation (M5b according to the FAB classification):

• makes up 3-6% of all acute non-lymphoblastic leukemias (ONLL);
• more than 20% of blasts have a characteristic monocytoid form of the nuclei, a weakly basophilic cytoplasm with a small granularity and vacuolization;
• blasts contain a significant amount of nonspecific esterase suppressed by sodium fluoride, a small amount of peroxidase and / or lipids in individual cells;
• blasts express the antigens CD33, CD13, CD14, CD15 and react with the ICA to lysozyme;
• t (9; ll), t (ll; 19), t (4; ll) are often detected with the formation of the MLL gene localized at llq23. In accordance with the WHO classification, these observations are categorized into an independent category of acute non-lymphoblastic leukemia (ONLL) with recurring anomalies.

Acute myelomonoblastic leukemia (M4 according to the FAB classification) – diagnosis

1) biclonal variant of acute myelomonoblastic leukemia:
• makes up 15-25% of all acute non-lymphoblastic leukemias (ONLL);
• blasts are represented by two types of cells – myeloblasts and monoblasts (biclonal variant);
• blasts express antigens CD33, CD13, CD14, CD15, react with MCA to peroxidase and lysozyme;
• llq23 or t (8; 21) anomaly can be detected;

2) bifenotypic variant of acute myelomonoblastic leukemia:
• makes up 1% of all acute non-lymphoblastic leukemias (ONLL);
• blasts are represented by a single cell type (bifenotypic variant);
• blasts are morphologically characterized as M2 myeloblasts;
• blasts contain peroxidase, lipids, granulocyte esterase and nonspecific esterase simultaneously suppressed by sodium fluoride in all cells;
• the immunophenotype of blasts is the same as that of cells in the biclonal variant;

3) myelomonoblastic with eosinophilia:
• M4eo accounts for about 10–12% of all acute non-lymphoblastic leukemia (ONLL);
• blasts are represented by two types of cells – myeloblasts and monoblasts;
• atypical eosinophils are present in the bone marrow, their number may exceed 6%. In eosinophilic myelocytes and metamyelocytes, large dark-colored granularity is detected;
• in blasts and eosinophils, inversion of chromosome 16 or t (l6; 16) is detected.

In accordance with the WHO classification, these observations are allocated to an independent category of acute non-lymphoblastic leukemia (ONLL) with recurring cytogenetic abnormalities.