Morphologically typical and atypical B-cell chronic lymphocytic leukemias display a different pattern of surface antigenic density

Recent evidences suggest that B-cell chronic lymphocytic leukemia (B-CLL) m ay have heterogeneous biological and clinical features. Immunological pheno type may be useful for distinguishing these different forms of disease. We used a quantitative flow cytometric approach to analyze the expression o f several membrane molecules (CD19, CD20, CD22, CD23, CD11c, CD5, CD79b) co mmonly used to diagnose and characterize B-CLL in a choort of 84 consecutiv e B-CLL patients diagnosed according to morphological and immunological fin dings. We found that morphologically so-called "atypical" B-CLL displayed a significantly higher number of CD20 and CD22 molecules than typical forms. On the other hand, CD19 was found to be more expressed in typical B-CLL, a lthough without reaching statistical significance. Finally, no difference w as detected with respect to CD23, CD79b, CD11c and CD5 number of molecules/ per cell between typical and atypical B-CLL. Other clinico-biological featu res, such as surface membrane immunoglobulin density, percentage of CD79b a nd FMC7 expression, peripheral blood lymphocytosis, trisomy 12 and advanced clinical stages were also found to be more frequent in atypical B-CLL. In conclusion, our data confirm the hypothesis that atypical B-CLL is a diseas e sustained by more mature B-cells, closely related but, at the same time, clearly distincted from neoplastic cells of typical B-CLL.