Several studies have shown that alveolar type II cells may be common precursors of both lung adenocarcinoma and SCLC.[12] Therefore, SCLC and adenocarcinoma cells could originate from the same cancer stem cells or progenitor cells.[13] Second, SCLC can result from the dedifferentiation of a previously well-defined cancer, which is similar to a mechanism known to occur in prostate cancer,[8,14] while the majority of transformed SCLCs retained the original EGFR-activating mutation, supporting this mechanism. Here, EGFR is linked to lung adenocarcinoma.