Cytogenetic studies in hairy cell leukemia.

Cytogenetic analyses were performed on cells from 17 patients with hairy cell leukemia stimulated with polyclonal B-cell activators (in 155 different cultures). No mitosis was obtained in samples from four cases (23.5%). Of 14 bone marrows, four (28.6%) showed mitoses, two with clonal abnormalities. All four samples from the spleen had mitoses with four clonal changes; eight of 13 (37.5%) blood samples had mitoses with three clonal changes. Of the polyclonal B-cell activators (PBA), lipopolysaccharide and protein A seemed to be effective for the detection of clonal abnormalities in hairy cell leukemia. Among the clonal aberrations, chromosomes #3, #10, and #17 were affected in two cases each; frequent numerical changes were monosomies of #10 and #17 and structural changes were deletions at band 3p21 (two cases), 6q-, and der(9)t(9;?)(p22;?). The chromosomal bands involved in structural changes were close to accepted constitutive fragile sites.