CD274 and neoplasm: Those PD-L1 IHC images were individually analyzed by thoracic subspecialty pathologist, and the main reasons can be summarized: (1) a small number of membrane-positive histiocytes or other infiltrated immune cells scattered inside and around the tumor nests were recognized as positive tumor cells; (2) a few of necrosis or apoptotic foci in tumor nests were recognized as positive tumor cells due to the non-specific staining.