KRAS and small cell lung carcinoma: Acquired resistance mechanisms to osimertinib in EGFR-driven NSCLC include MET amplification, EGFR C797S mutation, neuroendocrine differentiation, small-cell lung carcinoma histologic transformation, PD-L1 and KRAS amplifications and ESR1-AKAP12 and MKRN1-BRAF translocations, as well as BRAF V600 mutation.