TP53 and squamous cell carcinoma: KRAS hotspot mutations were more common in non-Asian patients than in Asian ones, previous and current smokers than in never-smokers, and patients without EGFR and BRAF mutations than in patients with EGFR and BRAF mutations; whereas TP53 hotspot mutations were more common in male patients than in female ones, patients with squamous cell carcinoma than in those with adenocarcinoma, and patients with poorly differentiated tumors than in well differentiated tumors.