The International Workshop on Chronic Lymphocytic Leukemia 2008 guidelines for the diagnosis of CLL requires a monoclonal B‐lymphocyte count of 5 x 109/L or more and a characteristic cell‐surface phenotype of B cells: the presence of CD5, CD19, and CD23, weak expression of CD20 and CD79b, and either kappa or lambda immunoglobulin light chains. The gene discussed is CD19; the disease is B-cell chronic lymphocytic leukemia.