While the contrast enhancement on MRI represents disruption of the blood-brain barrier (BBB), the increased FET uptake depicted by PET is caused by an overexpression of large neutral amino acid transporters (LAT) leading to an increased accumulation of FET in brain tumors which is not influenced by the BBB permeability (Stegmayr et al., 2017a; Stegmayr et al., 2017b). This evidence concerns the gene LAT and brain neoplasm.