For LUAD patients with EGFR mutations, EGFR-TKI therapy is now a standard treatment option, but a small number of LUAD patients experience phenotype changes after EGFR-TKI treatment; that is, the pathological type of the tumor changes from LUAD to SCLC, and the tumor progresses rapidly leading to death. The gene discussed is EGFR; the disease is neoplasm.