Additionally, to the rare occurrence of de novo small-cell lung cancers (SCLCs) in non-smokers (<2%), some SCLCs are believed to develop through the transformation of lung adenocarcinomas (LUADs), a type of non-small-cell lung cancer (NSCLC) that carries EGFR mutations or ALK alterations (~14%) [9,87,88,89]. Here, EGFR is linked to lung adenocarcinoma.