Currently, the mechanisms of resistance to osimertinib are mainly the occurrence of MET amplification (15–20%), the occurrence of a new mutation in the EGFR gene (10%), the acquisition of resistance mutations in the MAPKinase and PIK3 signaling pathways (10–15%), and a possible histological switch (10–15%) of cases towards small-cell lung cancer or a squamous NSCLC profile [23,24]. The gene discussed is EGFR; the disease is small cell lung carcinoma.