ASO Author Reflections: Clinical Implications of Programmed Death-Ligand 2 (PD-L2) Expression as an Independent Prognostic Marker in Lung Adenocarcinoma: Different Characteristics of PD-L2-Positive Patients from Those with Programmed Death-Ligand 1. - Takamori S; Takada K; Maehara Y (Annals of surgical oncology, 2019)