The Japanese Guideline for Diagnosis and Treatment of Lung Cancer 2022 (5) recommends that various genetic tests (EGFR/ALK/ROS1/BRAF/MET/RET/KRAS/NTRK) and programmed death-ligand 1 (PD-L1) tests should be conducted for stage IV NSCLC, and based on the results, the appropriate drug therapy is determined. This evidence concerns the gene RET and lung cancer.