[1174] A Flow Cytometric Protocol for Differential Diagnoses of Acute Monocytic Leukemia, Chronic Myelomonocytic Leukemia and Reactive Monocytosis

C Chen, RM Braziel, J Huang, G Fan. University of Maryland, Baltimore, MD; Oregon Health & Science University, Portland, OR

Background: Leukemias with a prominent monocytic component include acute myelomonocytic leukemia, acute monocytic leukemia (AMoL), and chronic myelomonocytic leukemia (CMML). Accurate diagnosis of these diseases is crucial for correct clinical management. Although flow cytometry (FC) is a highly sensitive and efficient method for evaluation of leukemias, its utility in diagnosing AMoL and CMML has to date been limited. The aim of this study is to identify a practical protocol that can distinguish immature from mature monocytes, and distinguish neoplastic from non-neoplastic monocytes.
Design: Using 4-color FC, we characterized monocytic cells from 75 leukemia samples (43 AMoL and 35 CMML), 37 non-neoplastic bone marrow or blood samples (15 from normal individuals and 22 from various reactive conditions). Monocytic differentiation and phenotypic features were determined with a panel of 11 antibodies, including CD13, CD14, CD15, CD34, CD36, CD45, CD56, CD64, CD91, CD117, and CD163.
Results: We compared expression patterns of various markers in AMoL, CMML and non-neoplastic monocytes, and found that (1) CD36 and CD64 were expressed by all monocytic cells and 50% of maturing granulocytes; the expression levels were higher in most but not all AMoL cells as compared to granulocytes; (2) absence or partial absence of CD14 or CD91 was characteristic of immature monocytes, and was found in 91% of AMoL but only in 14% of CMML; (3) diminished CD163 was seen in 78% of AMoL and 50% of CMML; (4) expression of CD56 was detected in 70% of AMoL and 33% of CMML; (5) under-expression of CD13 or CD15 was identified in 83% and 43% of AMoL, and 15% and 45% of CMML, respectively; (6) an increase in CD34+ or CD117+ cells (more than 7%) was seen in 38% of AMoL and 30% CMML. Although no single marker can reliably distinguish neoplastic from reactive monocytes, a combination of 11 markers showed that 98% of AMoL and 85% of CMML samples had at least two abnormal FC features whereas only 3% of non-neoplastic monocytes did.
Conclusions: Our studies show that a relatively simple FC protocol with 11 antibodies can distinguish neoplastic monocytes in AMoL and CMML from non-neoplastic monocytes in normal or reactive conditions with high sensitivity and specificity. In addition, loss of CD14 and/or CD91 is reliably identified in CD45dim immature monocytes, indicating that CD14 and CD91 are valuable markers in differentiation of AMoL and CMML.
Category: Hematopathology

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 197, Wednesday Afternoon