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. Here, PIK3CA is linked to small cell lung carcinoma.