CD 117: Lineage assigning marker in acute myeloid leukemias

Background: Acute Myeloid Leukemia (AML) is a malignancy of the cells of myeloid series characterized by the rapid growth of Myeloblasts. The diagnosis of AML is established by demonstration of more than 20% of the blood and/or bone marrow by leukemic myeloblasts. Immunophenotyping is one of the most useful tool for the confirmation, lineage assignment and subtyping of leukemias. This study was aimed to phenotype and classify acute leukemias by flow cytometry using commonly used markers for leukemia diagnosis and to establish whether CD 117 can be considered as a lineage specific marker in diagnosis and subclassification of AML.Methods: Flow Cytometric Immunophenotyping was employed for the study. The myeloid antibodies employed in AML in our study included - CD117, CD11c, CD13, CD15, CD33, CD34, CD36, CD41, CD65 and MPO.Results: In our study AMLs constituted 46% of all acute leukemias. CD117 positivity was seen in 86.56% of the French American British (FAB) category of AML. The blasts gated using CD45 v/s SSC revealed variable expression of CD34, CD13 and CD33. The expression of CD117 was consistent particularly in AML-M0, AML-M1 and AML M2.Conclusions: CD117 is virtually a myeloid blast marker with a high sensitivity, specificity and positive predictive value. Among the various myeloid markers like cMPO, CD13, CD33 and CD117, it is just CD117 that has got a tremendous reproducibility in AMLs. Besides CD117 is a surface marker unlike MPO thus easier to process, time saving and less prone to nonspecific binding.