PDCD1LG2 and head and neck squamous cell carcinoma: PD‐L2 expression is far less studied in human cancer than PD‐L1.8 Interaction of PD‐L2 with PD1 expressing T cells leads to an inhibition of T‐cell activation, similar to PD‐L1.6, 8 A recent immunohistochemical study could detect PD‐L2 expression in a variety of cancer types such as gastric cancer, lung cancer, and HNSCC.8 PD‐L2 expression was even present in some cases with missing PD‐L1 expression.8 In other malignancies such as primary mediastinal large B‐cell lymphoma and colorectal cancer, an increase in PD‐L2 expression31, 32 and a negative prognostic value32 was also shown.