Chromosome abnormalities in hairy cell leukaemia variant.

We describe chromosome abnormalities in 6 patients with hairy cell leukaemia (HCL) variant, a rare B-cell disorder with clinical and laboratory features intermediate between HCL and B-prolymphocytic leukaemia (B-PLL). All but one had marked splenomegaly and a raised white blood cell count (median 40 x 10(9)/l) with over 80% nucleolated hairy cells. These cells had a B-cell immunophenotype distinct from that of typical HCL. All patients but one are alive with stable disease with a median follow-up of 60 months. Numerical chromosome changes included loss of chromosomes 2, 3, 4, 6, 10, 19, 21, and X. three cases had translocations involving the immunoglobulin gene regions: t(14;17)(q32;q11), t(14;22)(q32;q11), and t(2;8)(p11.12;q24). Immunocytochemistry demonstrated the presence of the MYC protein in cells from the case with t(2;8) but not in two others. Other structural abnormalities included t(3;10)(q27;q22) and t(3;12)(q27;q13) in the same patient, der(17)t(7;10;17)(p11;q27;q22), t(1;3)(q25;p21), t(8;21)(p12;q11), t(17;21)(p11;p11), del(6)(q15), del(7)(q34), and del(14)(q24).