The transformation of EGFR-mutant adenocarcinoma to a SCLC histology was first reported in a 45-year-old woman with EGFR-mutant adenocarcinoma who underwent erlotinib treatment for 18 months before relapse with the features of SCLC, and positive immunostaining of neural cell adhesion molecule 1 (NCAM1), chromogranin A and synaptophysin [23]. The gene discussed is SYP; the disease is adenocarcinoma.