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Thread: Myeloblast, micromegakaryocyte, myeloid leukemia blood picture - blood histology atlas

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    Default Myeloblast, micromegakaryocyte, myeloid leukemia blood picture - blood histology atlas

    Clinical Features
    Patients with acute myeloid leukemia (AML) with minimal differentiation, AML without differentiation, and AML with differentiation usually present with evidence of bone marrow failure (ie, anemia, neutropenia, and/or thrombocytopenia). Patients with acute myelomonocytic leukemia (AMML) also typically present with anemia and/or thrombocytopenia, but AMML is often associated with a monocytosis that may be composed of mature monocytes, promonocytes, and/or monoblasts. Patients with acute monoblastic and monocytic leukemia often present with bleeding disorders, as well as with extramedullarymasses, cutaneous and gingival infiltration, and central nervous system (CNS) involvement. Patients with acute erythroid leukemia often present with profound anemia.

    Although patients with acute megakaryoblastic leukemia may present with evidence of bone marrow failure associated with pancytopenia, in some cases, thrombocytosis is present. Patients with acute basophilic leukemia often present with evidence of bone marrow failure, as is seen with the other types of AML described above; in addition, they may present with cutaneous involvement, organomegaly, lytic lesions, and symptoms related to hyperhistaminemia. Acute panmyelosis with myelofibrosis is associated with severe constitutional symptoms (ie, weakness, fatigue, fever, and bone pain) and, invariably, pancytopenia; the disease follows a rapidly progressive clinical course.

    AML without maturation
    In AML without differentiation, the predominant blast type, representing more than 90% of the nonerythroid cells, is a poorly differentiated myeloblast with one or more distinctive nucleoli. The blast population, termed blast type I, consists of blasts without any recognizable granules. In blast type II, some blasts have a few fine, azurophilic granules (numbering < 20). The presence of occasional Auer rods is consistent with the diagnosis of AML-M1. Because the blast population represents more than 90% of the cells, minimal differentiation is still present, but very few mature cells are found.

    AML with maturation
    AML with differentiation displays clear evidence of significant maturation, with abnormal differentiating cells ranging from promyelocytes to neutrophils. As defined by the World Health Organization (WHO) criteria, the percentage of blasts is at least 20% and less than 90%. The percentage of monocytic precursors must be less than 20% in the bone marrow, and there must be fewer than 5000/mL in the peripheral blood. In blast type III, greater than 20 granules must be present, with a central nucleus, no Golgi zone, and a fine chromatin with the classic blast characteristics (ie, blast type I without granules, blast type II with < 20 granules).

    Acute myelomonocytic leukemia
    In acute myelomonocytic leukemia (AMML), both granulocytic and monocytic precursors exist in varying proportions. For a diagnosis of AMML, the marrow monocytic component must account for 20% or more of the nonerythroid nucleated cells, but it cannot exceed 80%. In some cases, the bone marrow monocytic component may be less than 20%, but the peripheral blood must then demonstrate more than 5000 monocytes/µL.

    Acute monoblastic and monocytic leukemia
    In acute monoblastic leukemia, the marrow is almost exclusively composed of immature monoblasts with less than 20% promonocytes or mature monocytes (see the following image). The blasts are large (up to 30 mm or larger), with an abundant rim of cytoplasm; rarely, azurophilic fine granules are present, and vacuolated basophilic cytoplasm is sometimes seen. The nucleus is round to oval, with delicate, lacy chromatin.
    Myeloblast, micromegakaryocyte, myeloid leukemia blood attachment.php?s=bbb99ea4b3d55c3eeb6bd3043f86f907&attachmentid=393&d=1436366155

    Acute erythroid leukemia
    For a diagnosis of erythroid/myeloid leukemia, a minimum of 20% blasts must be present among the nonerythroid cells (myeloblastic type), and more than 50% of the erythroid precursors (among all the nucleated cells) must have dysmorphic features. In pure erythroid leukemia, a pure proliferation of erythroid progenitors is present, as can be seen in the image below.

    Acute megakaryoblastic leukemia
    Megakaryoblastic leukemia is a fulminant proliferative disease for which bone marrow biopsy is invaluable in establishing the diagnosis. The reason for this is that in only a few cases does the bone marrow aspirate show a significant (more than 20%) number of blasts. The aspirates frequently are very scant, owing to the marked myelofibrosis common in the disease.

    For these reasons, bone marrow biopsy specimens are needed. The sections may show many blasts or clusters of microkaryoblasts, as well as more mature megakaryoblasts. This is associated with an increase in the reticulin network and a corresponding decrease in the usual myeloid maturation. Megakaryoblastic fragments with changes in red blood cell morphologic structure and circulating small blasts, resembling either type I or type II blasts, may be found in the peripheral blood. The morphologic features of the blasts reveal cells that are pleomorphic; these cells may vary from very small forms with dense nuclear chromatin to large forms with prominent nucleoli. Cytoplasmic blebs may be found surrounding some blasts. In more mature cells, such as circulating micromegakaryocytes, these expansions look like platelets.

    In pediatric acute megakaryoblastic leukemia, the bone marrow aspiration is much more easily performed; the blasts may resemble lymphoblasts, but cytoplasmic blebs may be identified, as depicted below.

    Acute basophilic leukemia
    In acute basophilic leukemia, the blasts are characterized by moderately basophilic cytoplasm and a variable number of coarse basophilic granules. Mature basophils are sparse.

    Acute panmyelosis with myelofibrosis
    Acute panmyelosis with myelofibrosis is characterized by pancytopenia; leukoerythroblastosis may be evident in the peripheral blood. On bone marrow biopsy, hypercellularity with variable hyperplasia of erythroid precursors, granulocytes, and megakaryocytes is evident. There are foci of immature cells, including blasts, clusters of late-stage erythroid precursors, and increased dysplastic megakaryocytes associated with marked reticulin fibrosis. The marked fibrosis usually results in a "dry tap" upon aspiration.


    Last edited by Medical Photos; 08-14-2015 at 10:38 PM.

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