A 53-year-old male IV-stage NSCLC patient pleural fluid was sequenced by NGS; EGFR 19 exon deletions and EGFR T790M were both detected, and their variant frequencies were 15.66% and 4.58% covered, respectively, at around 2000× sequencing depth. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.