CD274 and diffuse large B-cell lymphoma: Similarly, no association was discovered between tumor PD-L1 expression (by IHC) and serum PD-L1 concentrations (by ELISA) in patients with diffuse large B-cell lymphomas and renal cell cancers, suggesting that tumor microenvironment, may also be involved in the regulation of serum PD-L1 levels [27,28].