Answer
AML with multilineage dysplasia is established by demonstrating at least 20% blasts and by identifying dysplastic features in at least 50% of cells in at least two bone marrow (BM) cell lines (ie, dysgranulopoiesis, dyserythropoiesis, or dysmegakaryopoiesis). [7] Features of dysgranulopoiesis include hypogranularity, hyposegmentation of granulocytes (ie, pseudo-Pelger-Huët forms), or other abnormalities of nuclear lobation or cytoplasmic granularity (eg, pseudo-Chediak-Higashi granules) (see the images below). As such, cytochemical staining, especially with myeloperoxidase (MPO), may be aberrant, because patients may develop an acquired MPO deficiency as part of the dysplastic process. [10, 11, 12]
Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). This image reveals a dysplastic promyelocyte with a cytoplasmic vacuole (left), blast (center), and dysplastic neutrophil with pseudo-Pelger-Huet anomaly and hypogranularity (right).
Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Dysgranulopoiesis demonstrating Chediak-Higashi-like granules (arrow) is shown.
Features of dyserythropoiesis include megaloblastoid forms, nuclear budding, irregular nuclear contours, nuclear fragmentation, multinucleation, karyorrhexis, ring sideroblasts, and cytoplasmic vacuolization (see the following images).
Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Numerous dysplastic erythroid cells are seen, demonstrating nuclear budding, irregular nuclear contours, and multinucleation.
Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). The bone marrow aspirate shows a binucleate erythroid precursor.
Features of dysmegakaryopoiesis include small size, nuclear hypolobation, nuclear hypersegmentation, and separated nuclear lobes (see the image below).
Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). The bone marrow core biopsy evaluation reveals dysmegakaryopoiesis with numerous small hypolobated megakaryocytes.
Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). A cluster of dysplastic megakaryocytes with small hypolobated nuclei is seen on a bone marrow aspirate smear preparation.
Rare cases of AML-MRC demonstrating basophilic differentiation have been reported. [13]
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). This image depicts dysgranulopoiesis: hypogranulosis.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). This image displays dysgranulopoiesis: vacuolization. Image courtesy of Rector and Visitors of the University of Virginia.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Dysgranulopoiesis demonstrating Chediak-Higashi-like granules (arrow) is shown.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Dyserythropoiesis is seen.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). The bone marrow core biopsy evaluation reveals dysmegakaryopoiesis with numerous small hypolobated megakaryocytes.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Dysmegakaryopoiesis in the multinucleated form is noted.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). This image reveals a dysplastic promyelocyte with a cytoplasmic vacuole (left), blast (center), and dysplastic neutrophil with pseudo-Pelger-Huet anomaly and hypogranularity (right).
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Note the dysplastic neutrophil with large pseudo-Chediak-Higashi granules.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). A dysplastic red blood cell with budding nuclei (left) is seen with a monocyte (center), and a blast (right).
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Numerous dysplastic erythroid cells are seen, demonstrating nuclear budding, irregular nuclear contours, and multinucleation.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). A cluster of dysplastic megakaryocytes with small hypolobated nuclei is seen on a bone marrow aspirate smear preparation.
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Pathology of Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Note the dysplastic neutrophil with large pseudo-Chediak-Higashi granules.
