PD-L1 IHC 22C3 pharmDx has since been approved as a companion diagnostic for use with pembrolizumab in other tumor types, including cervical cancer, esophageal squamous cell carcinoma (ESCC), gastric or gastroesophageal junction (GEJ) adenocarcinoma, head and neck squamous cell carcinoma (HNSCC), triple-negative breast cancer (TNBC), and urothelial carcinoma (UC; FDA label subsequently updated to remove PD-L1 tumor expression requirement) (13). Here, CD274 is linked to head and neck squamous cell carcinoma.