ROS1 and adenocarcinoma: Given that patients with adenocarcinoma and large cell histologies with NSCLC more commonly have genetic driver mutations than squamous cell carcinoma, patients with newly diagnosed nonsquamous NSCLC should routinely undergo genetic testing of their tumors for driver mutations in ALK, EGFR, and ROS1. Genetic testing of squamous cell NSCLC is not routinely performed unless patients have characteristics associated with genetic aberrations in ALK, EGFR, or ROS1 such as young age or nonsmoking patients.