FGFR1 and small cell lung carcinoma: In contrast, gene alterations most typically seen in the setting of SCLC include mutations of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), fibroblast growth factor receptor 1 (FGFR1), and phosphatase and TENsin homolog gene (PTEN) [35], which are addressed in subsequent sections.