EGFR and metastatic malignant neoplasm in the lymph nodes: Among these patients, EGFR T790 M mutation was detected in 23 patients via body fluids (19 pleural effusion, 2 ascites, and 2 cerebrospinal fluid), and in 69 patients in other specimen types, such as primary lesions, lymph node metastases, other tissue samples and plasma samples.