CD19 and B-cell chronic lymphocytic leukemia: Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are the most common B cell lymphoproliferative disorders originating from mature CD5+CD19+CD23+CD20+ B lymphocytes and are characterized by accumulation of neoplastic cells in peripheral blood, lymph nodes, spleen, and bone marrow (1, 2).