DISTRIBUTION OF THE CYTOGENETIC ABNORMALITY -CELL LYMPHOCYTOSIS - A FICTION STUDY IN 3 CASES(I(3)(Q10) IN PERSISTENT POLYCLONAL B)

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare entity cha racterized by a moderate but sustained lymphocytosis where some binucl eated or bilobulated circulating forms constitute, even if they are no t entirely specific, the cytological hallmark of the disease. An addit ional chromosome long arm i(3)(q10) has recently been reported as a re current cytogenetic aberration, contrasting with a usual polyclonal im munoglobulin expression. To determine more precisely the distribution of the chromosomal abnormality within the peripheral lymphocyte popula tion and study the relationship between the +i(3)(q10) and the bilobul ated character, we investigated three new cases of PPBL displaying the cytogenetic abnormality on the karyotype, using a technique of simult aneous fluorescence immunophenotyping and interphase cytogenetics (FIC TION). Mie demonstrated that the +i(3)(q10) was restricted to the B ly mphocytes, indepen dently of the kappa or lambda light chain isotype a nd was present in both bilobulated and non-bilobulated cells. Therefor e it is likely that the cytogenetic abnormality occurs at an early sta ge of lymphocyte differentiation in a precursor cell already committed to the B-cell lineage, before any rearrangement of immunoglobulin gen es has taken place.