[1190] New Flow Cytometry Markers for Distinguishing Acute Myeloid Leukemia, Acute Myelomonocytic Leukemia and Acute Monoblastic/Monocytic Leukemia

G Fan, J Huang, R Braziel, J Li, C Chen. Oregon Health and Science University, Portland, OR; Maryland University School of Medicine, Baltimore, MD

Background: Acute myeloid leukemia with monocytic differentiation represents pathologic entities of great clinical importance. Identification of monocytic components is traditionally based on morphology and cytochemical findings. However, morphologic evaluation is subjective. Cytochemical stain with nonspecific esterase (NSE) has a relatively high specificity, but 10-20% of acute monocytic leukemia (AMoL) cases are negative for NSE. Flow cytometry using CD14, CD36 and CD64 as monocytic markers had been shown to be useful. However, significant portion of AMoL show absence of CD14, low CD36 and low CD64 expression, which pattern is indistinguishable from granulocytic precursors. The aim of this study is to identify markers that allow differentiation between graunulocytic and monocytic precusors.
Design: Eight markers (CD49a, CD54, CD86, CD91, CD115, CD116, CD163 and CD172) as well as well-known monocytic/myeloid markers (CD14, CD36, and CD64) were chosen for 4-color flow cytometry study. We analyzed all markers on monocytic and granulocytic precusors/blasts from 15 normal bone marrow, 43 AMoL, 7 acute myelomonocytic leukemia (AMML), and 24 non-monocytic acute myeloid leukemia (NM-AML) samples.
Results: The studies show that all tested markers were expressed on normal monocytes. CD14, CD91 and CD163 had the highest specificity since they are not expressed by any of the NM-AML nor by normal maturing granulocytes; but they are highly expressed in AMoL cases (CD14 in 70%, CD163 in 80%, and CD91 in 93%). In addition, they often show abnormal expression pattern (dim or partial positivity) in AMoL. CD36 and CD64 had the highest sensitivity as they were expressed by all AMoL and AMML cases. However, their specificity is low since CD36 was detected in 36% of NM-AML and CD64 in 45% of NM-AML samples. Furthermore, CD64 shows same low expression in monocytic precursors as in granulocytes for about 20% of AMML/AMoL cases. CD49a, CD54, CD86, CD115, CD116 and CD172 showed no significant different staining pattern between NM-AML and AMoL.
Conclusions: Our studies have identified CD91 is a sensitive (100% sensitivity) and specific (93% specificity) monocytic marker. Its expression appears to be earlier than CD14 and represents the earliest monocytic lineage specific marker. CD91 should prove to be a useful marker for diagnosing leukemias with monocytic differentiation.
Category: Hematopathology

Tuesday, March 10, 2009 1:15 PM

Platform Session: Section D, Tuesday Afternoon