Immunolocalization of PD-1, PD-L1 in lung tumor tissue of patients with NSCLC. Immunohistochemical staining (IHC). Lung biopsy is obtained paraffin blocks, and are processed by IHC technique for antitumor expression of PD1 / PDL1.V PD-L1 immunostaining was classified into two groups according to intensity and extent: (a) negative, when no staining or positive staining was detected in <5% of the cells; and (b) positive, when membranous staining was present in P5% of the cells.