Yearley et al. reported that PD-L2 expression is observed in seven different tumor types (including renal cell carcinoma, bladder carcinoma, melanoma, non-small cell lung cancer, HNSCC, triple-negative breast cancer, and gastric carcinoma), especially in the patient samples absence of PD-L1 [22]. This evidence concerns the gene PDCD1LG2 and neoplasm.