Summary

This case from a 35-year-old male patient was one of acute promyelocytic leukemia (APL). APL is defined as an entity in the new WHO proposal for classification of AML based on the recurrent translocation t(15;17) detected by cytogenetic techniques. This case would be classified as M3 in the older FAB classification system. Cell surface markers are useful in establishing a myeloid origin of these cells and morphology coupled with cytogenetics allows a precise definition of the subtype. Side scatter versus CD45 shows a distinct population with high side scatter, in the region overlapping mature myeloid cells. This case was positive for CD45, CD13, CD15, CD33, weak for CD4 and negative for CD34 and HLA-DR. Cytoplasmic Myeloperoxidase (MPO) was positive, cCD79a and cCD3 were negative in the majority of cells. Based on morphology, M3 is characterized by the presence of predominately promyelocytes with heavy granulation. Auer rods are frequently seen. It is important to note that a hypogranular variant exists and the presence of an abnormal myeloid cell population that is CD13 or CD33 positive and negative for HLA-DR should be referred for cytogenetic analysis, specifically to rule out a t (15;17) translocation. Rapid definitive diagnosis is of particular importance in APL as cases with this rearrangement have been documented to show response to all-trans retinoic acid (ATRA). Both metaphase cytogenetics and interface Fluoresence in situ Hybridization (FISH) demonstrated the t(15;17) translocation, confirming this as a case of promyelocytic leukemia.

©2002 QMP–LS (Department of the OMA). All rights reserved.