Bimodal cell populations are common in chronic lymphocytic leukemia but do not impact overall survival

Flow cytometric histograms were evaluated for bimodal antigen expression on samples from 246 patients diagnosed with chronic lymphocytic leukemia (CLL) at University Hospitals of Cleveland, Cleveland, OH. Survival data were obtained, and the clinical significance of bimodality was evaluated using the Kaplan-Meier method and the log-rank test. Bimodal antigen expression was found in 107 cases (43.5%). CD38 and CD13 were the most common antigens to demonstrate bimodality at 14.5% and 12.9%, respectively, and CD20, CD11c, CD5, FMC-7, and surface immunoglobulin also were frequently bimodal. Bimodal antigen expression, the number of bimodal antigens, and bimodality of a specific antigen were not associated with decreased survival in patients with CLL, although bimodality for CD38 trended toward worse overall survival. Therefore, although bimodal antigen expression is common in CLL, the presence of bimodality does not seem to have significant prognostic importance