Histology versus cytology: PD-L1 testing in non-small cell lung cancer

Immune checkpoint inhibitors (ICIs) such as nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab have been developed to treat malignant tumors, including non-small cell lung cancer (NSCLC). ICIs inhibit programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) signaling between tumor cells expressing PD-L1 and cytotoxic T lymphocytes expressing PD-1.