KRAS and squamous cell lung carcinoma: Indeed, it is now well-established that lung adenocarcinomas driven by oncogenic EGFR or KRAS can undergo histological transformation to small cell lung cancer (SCLC; in the case of EGFR mutant tumors) or lung squamous cell carcinoma (for both EGFR and KRAS-driven tumors) upon treatment with targeted therapies (49–51).