Variant gene mutations of tumor cells often lead to different proliferation activities, and the location of the resulting metastasis may also differ.19 Recently, studies indicated that CSF was more representative of the EGFR mutation status in brain metastasis than peripheral blood and could better guide medical treatments.14 Nevertheless, that previous study did not evaluate the genetic characteristics of lung cancer with brain metastasis in cotesting of lung tumor tissue, brain metastases, peripheral blood, and CSF. This evidence concerns the gene EGFR and lung cancer.