A number of studies have shown that the specificity and sensitivity of ctDNA with EGFR mutation status detected in pleural effusion are close to, or even higher than, the tumor tissue.15, 16 Among 372 patients with EGFR mutation status confirmed by tumor tissue, 142 patients who did not receive any lung cancer treatment were enrolled in the study (72 EGFR mutants, 70 EGFR wild‐type), and their clinical features are summarized in Table 1. Here, EGFR is linked to neoplasm.