[1392] Immunophenotypic, Cytogenetic and Molecular Characterization of Biphenotypic B-Chronic Lymphocytic Leukemia.

Huan-You Wang, Elizabeth H Broome, George F Widhopf, Marie L Dell'Aquila, Laura Z Rassenti, Thomas J Kipps. UC San Diego, La Jolla, CA

Background: B-chronic lymphocytic leukemia (CLL) is the most common leukemia of adults in the western countries; however, there is no detailed immunophenotypic, cytogenetic and molecular study of biphenotypic CLL.
Design: A search of the UCSD flow cytometry database revealed 5 cases of biphenotypic CLL at the time of diagnosis. Flow cytometry, karyotype and fluorescence in situ hybridization (FISH) of the bone marrow were performed. Rearrangement of immunoglobulin heavy chain variable (IgHV) regions using primers covering IgHV1 through IgHV6 subfamilies was investigated by the polymerase chain reaction (PCR).
Results: All 5 cases were male with median age of 63 years. All but one (case #5) had positive CD23 and aberrant CD5 co-expression among CD19(+) B-cells, and all 5 cases have simultaneous kappa- and lambda-positive populations in the bone marrow aspirate. The distribution of CD5+/CD19+/kappa+:CD5+/CD19+/lambda+ populations at the time of diagnosis from the first 4 cases were 11%:46%, 60%:29%, 22%:28%, and 32%:2.6%, respectively. The kappa:lambda population in the case #5 is 30%:31%. Cases #1 and #2 had one and two post-chemotherapy followups, respectively. While the percentage of CD5+/CD19+/K+ to CD5+/CD19+/L+ CLL populations varied in post-chemotherapy samples, the distribution pattern of CD5+/CD19+/K+ to CD5+/CD19+/L+ remained similar to the diagnostic ones (kappa < lambda in case #1, kappa > lambda in case #2). Conventional karyotyping revealed no clonal abnormalities among 4 cases (cases #1, 3-4 & 5) analyzed; however, FISH showed the biallelic and monoallelic loss of 13q14.3 in 29% and 28.5% of cells, respectively, in case #1; monoallelic loss of the ATM gene at 11q23 locus in 46% of cells in case #2; trisomy 12 in 9.5% in case #3, monoallelic loss of p53 at 17p13.1 in 22% of the cells in case #5, but no abnormal FISH findings in case #4. PCR demonstrated a single IgHV rearrangement pattern in cases #1, #2, #4 and #5 except case #3, which showed a dual IgHV rearrangement pattern.
Conclusions: All 5 biphenotypic CLL contained simultaneous kappa- and lambda-positive populations. There was genetic diversity ranging from normal to deletion of the p53. Eighty percent (4/5) of the cases showed a single IgHV rearrangement pattern, supporting the notion that the 2 biphenotypic CLL populations were originated from a single neoplastic clone, 20% (1/5) of the cases showed dual IgHV rearrangement pattern, supporting the notion that the 2 biphenotypic CLL populations were originated from 2 independent clones.
Category: Hematopathology

Wednesday, March 2, 2011 9:30 AM

Poster Session V # 168, Wednesday Morning

 

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