Prolymphocytic leukemia: flow microfluorometric, immunologic, and cytogenetic observations.

Cells isolated from four patients with prolymphocytic leukemia were evaluated by surface markers, cytogenetics, and flow microfluorometric analysis of cell size and DNA content. All four patients had B-cell markers with a high density of IgM, kappa type, and Ia-like antigen. Less intense staining for surface IgD was also observed. In each patient studied, chromosomal modes were in the hypodiploid or near-diploid range. Despite the karyotypic abnormalities, the cellular DNA content, as determined by flow microfluorometry, was within the normal limits in all cases. This suggests that the variability in chromosome numbers seen in these patients may reflect an abnormality in DNA package rather than differences in total DNA content. The modal electronic cell size of the prolymphocytes, determined by light scatter, was readily distinguishable from that of normal peripheral blood lymphocytes and the lymphocytes of chronic lymphocytic leukemia. Fewer than 4% of the peripheral prolymphocytes had S-phase DNA content, a finding consistent with the chronic nature of this leukemia.