Heterogeneity and clinical relevance of the intensity of CD20 and immunoglobulin light-chain expression in B-cell chronic lymphocytic leukemia

In a prospective study, peripheral lymphocytes of 93 previously untreated patients with B-cell chronic lymphocytic leukemia (B-CLL) were evaluated with flow cytometry for the intensity of CD20 and surface immunoglobulin (sIg) light-chain (LC) expression. Molecules of equivalent soluble fluorescence were used to classify intensity of surface antigen expression as 'strong,' 'moderate,' or 'weak.' Despite reproducible morphological consistency with B-CLL, variability in intensity of CD20 and sIg light chain expression was substantial. CD20 intensity was classified as weak in 62% of patients, moderate in 12%, and strong in 26%. Expression of sIg light chain was weak in 76% and strong in 24%. The patients were followed up for a median of 3.1 years. Intensity of expression of CD20 and sIg light chain was not correlated with any presenting feature at the time of phenotyping, including clinical stage and degree of lymphocytosis or organomegaly. Similarly, clinical course of the disease, time to progression, response to therapy, and overall and treatment-free survival were not predictable from the intensity of CD20 or sIg light chain expression. In conclusion, bright expression of CD20 or sIg light chain is not an unusual feature in B-CLL and may not influence clinical presentation or short-term prognosis.