RB1 and small cell lung carcinoma: Unfortunately, he returned to the local hospital with supportive care and died shortly after.<h4>Conclusion</h4>Based on these observations, we proposed that LCNEC and SCLC components in this patient may have a common clonal origin with dual mutations in <i>TP53</i> and <i>RB1</i>, while the chromosome instability may cause multiple independent conversion that leads to LCNEC or SCLC morphologies.