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

98 Abnormalities of the White Cell SeriesAcute Promyelocytic Leukemia (FAB Classification Type M 3 and M 3 v). Thecharacteristic feature of the cells, which are usually quite large with variablystructured nuclei, is extensive promyelocytic granulation. Auer rodsare commonly present. Cytochemistry reveals a positive peroxidase reactionfor almost all cells. All other reactions are nonspecific. Acute leukemiawith predominantly bilobed nuclei is classified as a variant of M 3 (M 3 V ).The cytoplasm may appear either ungranulated (M 3 ) or very stronglygranulated (M 3 V ).Acute Myelomonocytic Leukemia (FAB Classification Type M 4). Given theclose relationship between cells in the granulopoietic and the monocytopoieticseries (see p. 3), it would not be surprising if the these two systemsshowed a common alteration in leukemic transformation. Thus, acute myelomonocyticleukemia shows increased granulocytopoiesis (up to morethan 20% myeloblasts) with altered cell morphologies, together with increasedmonocytopoiesis yielding more than 20% monoblasts or promonocytes.Immature myeloid cells (atypical myelocytes to myeloblasts)are found in peripheral blood in addition to monocyte-related cells. Cytochemically,the classification calls for more than 3% peroxidase-positiveand more than 20% esterase-positive blasts in the bone marrow. M 4 is similarto M 2 ; the difference is that in the M 4 type the monocyte series isstrongly affected. In addition to the above characteristics, the M 4Eo variantshows abnormal eosinophils with dark purple staining granules.