[1554] Spectrum of Immunophenotypic Aberrancies in Myelomonocytic Antigens in Chronic Myelomonocytic Leukemia: Novel Identification of CD11c Underexpression

Payal Sojitra, Pranav Gandhi, Yanxia Li, Girish Venkataraman. Loyola University Medical Center, Maywood, IL

Background: The diagnosis of CMML can be challenging and the detection of immunophenotypic aberrancies (IPAb) via flow cytometry (FCM) may aid in better establishing a neoplastic monocytic proliferation. While several previous studies have described IPAbs in CMML monocytes by FCM, published data using 5-color FCM are limited.
Design: We retrieved 22 cases (19 bone marrows[BM], 3 peripheral blood) of CMML. Marrow histopathology and concurrent 5-color flow cytometry data were reviewed. Additionally, 5 BMs submitted for lymphoma staging without evidence of disease were used as a controls. For FCM, two monocyte-specific tubes (CD45-PC7/CD11c-PE/CD64-FITC/CD14-ECD/CD22-PC5; CD45-PC7/CD33-PE/CD15-FITC-HLA-DR-ECD/CD34-PC5) were used besides CD2, CD56, CD38 and markers for B- and T-cells. Flow cytometry list mode files were examined using the CXP (Beckman-Coulter Inc.) software gating on the monocytes using either CD45/side scatter (SSC), forward scatter (FS)/SSC or CD14/CD64 in a small subset of cases.
Results: There were 21 dysplastic-CMML and one proliferative-CMML. Nineteen of 22 showed dysplastic morphologic changes in either megakaryocytic, myeloid or erythroid lineages. The monocytes in flow samples ranged from 4-35% of all live events. At least one IPAb was found on the monocytes in 18 of 22 cases (81%). Of these 18 cases, 3 showed only 1 IPAb, 7 evidenced two IPAb, 6 with 3 IPAb and 2 cases notably showed 5 different IPAb. In order of frequency, the most common IPAb was aberrant CD56 expression (12 cases), followed by under expression of CD11c (7 cases; figure 1; arrow indicates monocytes), aberrant expression of CD2 (6 cases), under expression of CD33 (6 cases), under expression of CD38 (4 cases), CD14mod (3 cases), homogeneous CD15 and HLA-DR under expression in 2 cases each. None of the 5 control marrows showed any of these aberrancies. Notably fifteen cases showed markedly decreased granulocyte SSC, one of which represented a case without any other IPAb.

Conclusions: This study identified novel CD11c underexpression on monocytes in over 33% of CMML and additionally extends and confirms IPAb previously identified on CMML monocytes in other studies.
Category: Hematopathology

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 229, Wednesday Morning


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