[1246] Aberrant CD56 Expression in Myelomonocytic Cells Correlates with Chromosomal Aberrations in Chronic Idiopathic Myelofibrosis (CIMF/PMF)

P Lin, B Feng, JL Jorgensen, S Verstovsek. UT MD Anderson Cancer Center, Houston, TX

Background: CIMF/PMF often exhibits granulocytic and megakaryocytic hyperplasia. Flow cytometry (FC) immunophenotypic features of myeloid cells in CIMF are not well documented. The aim of the study is to assess the frequency of the aberrant phenotypes in myelomonocytic cells in CIMF and correlate the results with JAK2 and cytogenetics.
Design: 79 CIMF cases with JAK2 status and karyotypes characterized were identified from 2000 to 2007. Bone marrow aspirates of 35 cases were analyzed by FC with a panel that included CD56. The percentage of myelomonocytes positive for CD56 and their mean fluorescence intensity (MFI) were assessed and compared with the values for 17 cases of MDS (RCMD or RAEB-1) with myelofibrosis, and 20 non-CMPD controls. The results were correlated with hematologic parameters, prior therapy, JAK2 mutation and cytogenetics.
Results: Aberrant phenotypes were observed in 26 of the 35 (80%) CIMF cases analyzed, including CD56 overexpression in granulocytes and/or monocytes, and/or decreased side scatter in granulocytes. The MFIs of the CD56 expression by both granulocytes and monocytes in CIMF cases are significantly higher than those of the controls (p<0.001) and are comparable to or higher than that of MDS with myelofibrosis. JAK2V617F and chromosomal aberrations were found in 18 (51.4%) and 15 (42.9%) cases, respectively. The JAK2V617F alleles burdens range from 19%-93% (Median 45%). Aberrant CD56 expression statistically correlates with cytogenetic aberrations.

Table 1. CD56 Mean Fluorescent Intensity (MFI) of Granulocytes and Monocytes Correlates Positively with Chromosomal Abnormalities in CIMF/PMF

	Gran CD56 MFI(Mean+SD)	Mono CD56 MFI(Mean+SD)	SSC MH(Mean+SD)
CIMF: Abnormal karyotype (n=15)	28.01+27.45	28.35+32.01	596.7+175.5
CIMF: Normal karyotype (n=20)	12.00+9.73	36.65+27.97	697.2+119.7
CIMF: JAK2v617+ (n=18)	27.12+27.83	27.81+32.22	693.0+113.0
CIMF: JAK2v617F- (n=17)	11.23+7.88	38.04+26.37	672.9+158.5
MDS/MF (n=17)	10.60+8.96	38.04+26.37	775.1+195.7
Control Group (n=20)	4.42+1.14	9.15+4.91	920.3+78.4

SSC MH--Side scatter median height


Conclusions: As seen in MDS with myelofibrosis, myelomonocytic cells in more than half of CIMF cases exhibit aberrantly increased CD56 expression. CD56 overexpression correlates strongly with the presence of cytogenetic aberrations but not with JAK2 mutation.
Category: Hematopathology

Wednesday, March 11, 2009 1:00 PM

Poster Session VI # 169, Wednesday Afternoon