A previous investigation reported on the concentrations of three tumor markers, CEA, cytokeratin 19 fragments (CYFRA 21-1), and neuron-specific enolase (NSE), in CSF of 35 lung cancer patients with meningeal carcinomatosis of lung cancer and 35 patients with benign brain tumors [153]. This evidence concerns the gene ENO2 and leptomeningeal metastasis.