Genetic and immunophenotypic profile of IGH@ rearrangement detected by fluorescence in situ hybridization in 149 cases of B-cell chronic lymphocytic leukemia

Abstract

Recent studies have shown a higher frequency of immunoglobulin heavy (IGH@) locus rearrangement in B-cell chronic lymphocytic leukemia (B-CLL) than previously reported. However, association of the IGH@ rearrangement with specific chromosomal abnormalities and immunophenotypic markers in B-CLL is still under further investigation. In this study, we analyzed 149 bone marrow aspirate or peripheral blood specimens from patients diagnosed with B-CLL, evaluated by four different laboratory studies: morphology examination, three- or four-color flow cytometry analysis, conventional cytogenetics, and fluorescence in situ hybridization (FISH) with a dual-color, break-apart IGH@ probe in addition to a B-CLL FISH probe panel for del(11)(q22) ATM, del(13)(q14.3), del(17)(p13) TP53, and +12. An IGH@ rearrangement was found by FISH in 24 cases (16.0%). Of these 24 cases, 16 (67%) contained chromosomal abnormalities, including t(14;19)(q32;q13.2), t(8;14)(q24;q32), and t(14;18)(q32;q21). In addition, a cryptic deletion of the immunoglobulin heavy variable region (IGHV) was revealed. Using 30% as the cutoff for positive CD38 expression, 22 of the 24 cases (92%) were positive for CD38. The present results further confirm that IGH@ rearrangement is not a rare genomic abnormality in B-CLL, and also show both that t(14;19)(q32;q13.2) is the most common cytogenetic change involving IGH@ rearrangement detected by FISH in B-CLL and that IGH@ rearrangement is correlated with CD38 expression. It is appropriate to include an IGH@ probe in the FISH panel for B-CLL diagnosis.