[1306] Biologic Characteristics of Monoclonal B-Cell Lymphocytosis Detected by Routine Clinical Flow Cytometric Testing.

Zaibo Li, Steven H Swerdlow, Urvashi Surti, Fiona E Craig. Univ. of Pittsburgh Medical Center, PA

Background: Monoclonal B-cell lymphocytosis (MBL) should be considered when a chronic lymphocytic leukemia (CLL)-like phenotype is identified but B-cells are <5 x109/L. MBL encompasses cases identified by population screening, in which B-cells are often <0.5 x109/L and frequently <0.05 x109/L, and those identified through investigation of lymphocytosis, in which B-cells are frequently >1.9 x109/L. Previous studies have suggested that these two groups differ biologically, and higher count cases more closely resemble CLL. However, it is difficult to translate this into clinical flow cytometry (FC) practice.
Design: In order to further investigate the relationship between CLL and MBL, clinical and biologic features were compared for specimens with a CLL-like phenotype identified using routine FC immunophenotyping (Table).

CharacteristicsMBL (%)CLL (%)p-value
Sex  0.168
Male22 (55.0)95 (63.3) 
Female18 (45.0)55 (36.7) 
Age  0.054
≥60 years34 (85.0)109 (72.7) 
<60 years6 (15.0)41 (27.3) 
Median B cell count (x109/L)2.4913.16 
ZAP-70 (n=190)  0.073
>20%10 (25.0)56 (37.3) 
≤20%30 (75.0)94 (62.7) 
CD38 (n=190)  0.429
>30%13 (32.5)51 (34.0) 
≤ 30%27 (67.5)99 (66.0) 
Cytogenetics (n=89)   
Isolated Del 13q144 (30.8)28 (36.8)0.337
Trisomy 124 (30.8)15 (19.7)0.185
Del 11q220 (0)7 (9.2)0.128
Del 17q130 (0)4 (5.3)0.199

Results: 40 MBL and 150 CLL were identified. MBL included the following B-cell counts (x109/L): >1.9 (22), 1.9 to >0.5 (11), 0.5 to >0.05 (6) and <0.05 (1). No significant difference was identified between CLL and MBL, either as a group or divided by range of B-cell count. ZAP-70 showed concordance with CD38 in MBL (67.5% concordant) and CLL (65%). MBL with isolated deletion 13q14 were negative for ZAP-70 and CD38 and those with trisomy 12 were either positive for ZAP-70 and CD38 or CD38 only. Cytogenetic markers associated with poor prognosis (del 11q22 or del 17p13) were absent in MBL but present in 14.7% of CLL.
Conclusions: MBL identified in a clinical laboratory using routine FC demonstrates a broad range of B-cell count, overlapping those previously reported for population screening and investigation of lymphocytosis. Although cytogenetic markers associated with a poor prognosis were not identified, MBL shared many biologic features with CLL. Therefore, the utility of the 5 x109/L B-cell threshold remains uncertain.
Category: Hematopathology

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 187, Monday Morning


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