TTF1 and non-small cell lung carcinoma: It has been broadly acknowledged that CK (7) positive refers to the epithelial-original cancer especially the lung tissues.[20,21] The National Comprehensive Cancer Network and Pan-Asian European Society for Medical Oncology guidelines of NSCLC strongly recommended to ascertain LUAD by TTF-1 and Napsin A.[22,23] Moreover, EGFR 19DEL has been proved 1 of the most common mutated forms in LUAD.[24] Combining the medical history, IHC and genetic testing results, we concluded that the metastatic intracranial adenocarcinoma was derived from LUAD.