Mechanisms of acquired resistance to osimertinib are known to be heterogenous, including EGFR C797X; loss of T790 M; SNV of PIK3CA, KRAS, and BRAF; and amplification of MET. 24, 25In addition to these variants, epithelial‐to‐mesenchymal transition, manifested as small cell carcinoma (SCLC) transformation, is not an infrequent cause of EGFR‐TKI resistance. Here, PIK3CA is linked to small cell lung carcinoma.