Although gene amplification of MET or HER2 and transformation to small cell lung cancer have been identified in osimertinib-resistant tumors5–8, and cytokines such as tumor necrosis factor-α (TNF-α) and interferon have been associated with the development of EGFR-TKI resistance in NSCLC9,10, the mechanisms underlying most cases of osimertinib resistance have remained unclear. Here, TNF is linked to small cell lung carcinoma.