In this setting, CD38 expression is commonly found on many immunosuppressive cell types, including (i) regulatory T cells (T regs) (ii) regulatory B cells (B regs), (iii) myeloid-derived suppressor cells (MDSCs) and (iv) the CD16−CD56bright NK cell subset, whose importance in tumor—microenvironment interactions is being increasingly recognized. This evidence concerns the gene CD38 and neoplasm.