CD274 and head and neck cancer: In line with our data, multiple earlier studies have described associations between tumoral PD-L1 expression and a high density of tumor-infiltrating lymphocytes (TILs) in breast cancer [52,53,54] and in other tumors such as head and neck cancer [55], non-small cell lung cancer [56], and gastric cancer [57] as well as a link between a high density of TILs and favorable prognosis in breast cancer [58] and several other tumor entities [59].