CD274 and lymphoma: PD‐1 and its ligands PD‐L1 and PD‐L2 are often expressed in tumor or neoplastic microenvironments, including epithelial malignancies, classical Hodgkin lymphoma (HL), and NHL, although the expression of PD‐L1 seems to vary significantly among lymphoma subtypes (Andorsky et al., 2011; Chen et al., 2013; Wilcox et al., 2009).