SURFACE-IMMUNOGLOBULIN DENSITY IN THE DIFFERENTIAL-DIAGNOSIS OF B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA AND LEUKEMIC IMMUNOCYTOMA

Using flow cytometry peripheral blood samples of 37 consecutive patients with B-cell chronic lymphocytic leukemia (B-CLL) and 17 consecutive patients with leukemic immunocytoma (IC) were studied in order to determine quantitative differences in the surface immunoglobulin (slg) density. In 8/37 (21.6%) cases of B-CLL and 1/17 (5.9%) cases of IC slg staining remained in the control level. Analysis of slg-positive cases demonstrated a close association between the amount of slg and diagnosis: per case the mean calculated fluorescence intensity for IC lymphocytes was 209.7 arbitrary linear intensity units (IU) (median: 156.4, standard error of the mean (SEM): 53.7) and for B-CLL lymphocytes 10.8 IU (median: 7.3, SEM: 1.1; p < 0.0001). Altogether, 94.6% of all B-CLL patients and 76.5% of all IC patients were correctly classified when a cut-off point was fixed at a mean fluorescence intensity value of 20.0 IU. The percentage of leukemic cells as characterized by CD19 and HLA-DR reactivity was significantly lower in cases of IC (p < 0.03 and p < 0.01, respectively). In both entities disease progression occurred more frequently in advanced stages (II-IV) according to the Rai classification (p < 0.01). In progressive disease rather than in stable disease circulating T lymphocytes were shown to express decreased amounts of surface CD3 antigen (p < 0.02). We conclude that the quantitative assessment of surface antigens in addition to their qualitative characterization provides accurate information. In particular, the diagnostic discrimination between B-CLL and IC may be improved by determining the lymphocytes' slg amount.