PDL1 and CD3 immunohistochemistry was carried out on 3 μm full face sections using PD-L1/CD274 (SP142) antibody (Spring Bioscience, CA, USA) at 1 : 40 dilution and CONFIRM anti-CD3 (2GV6) rabbit monoclonal antibody (Ventana, UK) respectively. In addition OptiView amplification kit was used for PDL1 antibody. Staining was carried out on Ventana Benchmark XT platform with the OptiView Universal DAB Detection Kit (Ventana Medical Systems, Burgess Hill, UK).
PDL1 scoring was performed separately for peritumoural lymphoid follicles (PLF), intra-tumoural lymphoid cells (ILC) and tumour epithelial cells (TEC). Scoring criteria used was 0 (negative) for no cell staining and 1 (positive) for any number of cells staining. CD3 staining, assessed in ILCs only, was scored semi-quantitatively using a three tiered scoring system (1 for the lowest counts observed and 3 for the highest).
PDL1 scoring was performed separately for peritumoural lymphoid follicles (PLF), intra-tumoural lymphoid cells (ILC) and tumour epithelial cells (TEC). Scoring criteria used was 0 (negative) for no cell staining and 1 (positive) for any number of cells staining. CD3 staining, assessed in ILCs only, was scored semi-quantitatively using a three tiered scoring system (1 for the lowest counts observed and 3 for the highest).