CD5 and B-cell chronic lymphocytic leukemia: CLL is a malignancy of CD5+ B cells that is characterized by the accumulation of small, mature-appearing neoplastic lymphocytes in the blood, marrow and secondary lymphoid tissues, resulting in lymphocytosis, leukemia cell infiltration of the marrow, lymphadenopathy and splenomegaly (Kipps et al., 2017)