CD38 and hematologic disorder: Monoclonal antibodies approved by the FDA in the last decade for the treatment of hematological malignancies target cluster of differentiation 19 (CD19), cluster of differentiation 20 (CD20), cluster of differentiation 38 (CD38), signaling lymphocyte activation molecule family member 7 (SLAMF7), and programmed death receptor-1 (PD-1).