CD274 and head and neck squamous cell carcinoma: As shown in Figure 2A, PD-L1 expression levels were significantly higher than in adjacent normal tissues in the following cancers: cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC), cholangiocarcinoma (CHOL), esophageal carcinoma (ESCA), head and neck squamous cell carcinoma (HNSC), and stomach adenocarcinoma (STAD).