Cytogenetic studies on prolymphocytic leukemia. 1. B-cell prolymphocytic leukemia.

We describe clonal chromosome abnormalities in 13 new cases of B-cell type prolymphocytic leukemia (B-PLL) investigated using pokeweed, lipopolysaccharide B, TPA (phorbol ester), and Epstein-Barr virus (EBV) as mitogens. B-PLL showed a much better response to all four mitogens when compared with B-cell chronic lymphocytic leukemia (B-CLL). A 14q+ was the most frequent abnormality and was observed in 7 of the 13 cases. A t(11;14)(q13;q32) was observed in 2 patients in this series and in 2 cases from a previous series of 9 patients studied in this laboratory, giving an incidence in B-PLL of 18% for this abnormality. The more frequent rearrangement of both IgH genes in B-PLL when compared to B-CLL may predispose to a higher incidence of 14q+ in B-PLL. Trisomy 12 which is a feature of B-CLL was observed in one case in the present series. Other abnormalities of chromosome 12 included 12p-(p12-13) in 2 cases and t(12;14)(q22;q32) in 1 case. The t(6;12) previously described as a specific abnormality in B-PLL was not observed in the 22 cases (13 present series, 9 previous series) studied in our laboratory.