CD274 and cancer: Both lymphocytes and antigen presenting cells (i.e. macrophages, monocytes and dendritic cells) are able to express both PD-1 and PD-L1 in malignancies[32] Since it is troublesome to differentiate large lymphocytes from small macrophages and monocytes based solely on morphologic examination, we decided to adapt a summary measure and term them as leukocytes.