Color Atlas of Hematology - Practical Microscopic and Clinical ...

102Abnormalities of the White Cell SeriesAcute Megakaryoblastic Leukemia (FAB Classification Type M 7 )This form of leukemia is very rare in adults and occurs more often inchildren. It can also occur as “acute myelofibrosis,” with rapid onset oftricytopenia and usually small-scale immigration into the blood of dedifferentiatedmedium-sized blasts without granules. Bone marrowharvesting is difficult because the bone marrow is very fibrous. Only bonemarrow histology and marker analysis (fluorescence-activated cellsorting, FACS) can confirm the suspected diagnosis.The differential diagnosis, especially if the spleen is very enlarged,should include the megakaryoblastic transformation of CML or osteomyelosclerosis(see pp. 112 ff.), in which blast morphology is very similar.AML with DysplasiaThe WHO classification (p. 94) gives a special place to AML with dysplasiain two to three cell series, either as primary syndrome or following a myelodysplasticsyndrome (see pp. 106) or a myeloproliferative disease (seepp. 114 ff.).Criteria for dysgranulopoiesis: 50% of all segmented neutrophilshave no granules or very few granules, or show the Pelger anomaly, or areperoxidase-negative.Criteria for dyserythropoiesis: 50% of the red cell precursor cellsdisplay one of the following anomalies: karyorrhexis, megaloblastoidtraits, more than one nucleus, nuclear fragmentation.Criteria for dysmegakaryopoiesis: 50% of at least six megakaryocytesshow one of the following anomalies: micromegakaryocytes, morethan one separate nucleus, large mononuclear cells.Hypoplastic AMLSometimes (mostly in the mild or “aleukemic” leukemias of the FAB orWHO classifications), the bone marrow is largely empty and shows only afew blasts, which usually occur in clusters. In such a case, a very detailedanalysis is essential for a differential diagnosis versus aplastic anemia (seepp. 148 f.).