TP53 and small cell lung carcinoma: Tobacco smoking is the leading risk factor for SCLC which accounts for ≥ 95% of the whole population in SCLC patients.3 SCLC is a kind of neuroendocrine tumor (NET) clinically characterized by a rapid growth and early distant metastasis.3 It is usually diagnosed at the extensive stage (ES) with prognosis poor.3 As a highly aggressive subtype of lung NET, SCLC is characterized by deletion of multiple tumor suppressor genes, such as mutations in TP53 and RB1.4 This characteristic also determines that SCLC is difficult to be treated with target therapy precisely.