Typical and atypical chronic lymphocytic leukemia differ clinically and immunophenotypically

We compared the features of 17 cases of atypical chronic lymphocytic leukem ia (aCLL) with those of a clinical control group of 24 cases of CLL. Quanti tative flow cytometric data, available for 12 cases, were compared with an immunophenotypic control group of 58 cases using a relative fluorescence in dex for CD5, CD23, CD79b, and surface immunoglobulin light chain (sIg). Compared with the clinical control group, patients with aCLL had a higher m ean WBC count and a lower platelet count. Patients with aCLL had a signific antly higher probability of disease progression. Compared with an immunophe notypic control group of 58 CLL cases, 12 cases of aCLL demonstrated signif icantly higher expression of CD23. There was no significant difference in e xpression of sIg, CD79b, or CD5 between the groups. CD38 expression was not ed in only 1 (9%) of 11 tested cases; 2 (18%) of 11 cases had trisomy 12. a CLL can be distinguished from typical CLL morphologically, clinically, and immunophenotypically. Atypical morphologic features in CLL seem to be a mar ker of aggressive clinical behavior.