Inter‐ and intraobserver agreement of programmed death ligand 1 scoring in head and neck squamous cell carcinoma, urothelial carcinoma and breast carcinoma

Aims Programmed death‐ligand 1 (PD‐L1) expression by tumour cells (TC) is a mechanism for tumour immune escape through down‐regulation of antitumour T cell responses and is a target for immunotherapy. PD‐L1 status as a predictor of treatment response has led to the development of multiple biomarkers with different reference cut‐offs. We assessed pathologist consistency in evaluating PD‐L1 immunopositivity by examining the inter‐ and...