PIK3CA and squamous cell carcinoma: In small-cell lung cancer (SCLC), TP53 mutations were less frequent in never-smokers than in current/former smokers (59% vs. 85%, p < 0.001), whereas EGFR (26% vs. 2.6%, p < 0.001), PIK3CA (15% vs. 3.6%, p = 0.023), and OS9 mutations (5.6% vs. 0%, p = 0.009) were more common in never-smokers [110], In squamous cell carcinoma (SCC), STK11 mutations were observed more frequently in never-smokers than in smokers (50% vs. 7%, p = 0.026) [111].