Firstly, we found that the serum concentrations of CTSF and FBLN1 in NSCLC BM patients were significantly higher than those in NSCLC patients without BM, patients with a primary brain tumour, and healthy individuals, which were not affected by the presence or absence of other organ metastasis or whether the patient had undergone lung lesion surgery before the BM. Here, CTSF is linked to brain neoplasm.