Gliomas are a type of brain tumor characterized by a poor prognosis. In order to improve this prognosis, as much of the tumor as possible must be removed safely during the neurosurgical operation. However, especially in the case of slow-growing, low-grade gliomas, it is often difficult to distinguish diseased tissue from healthy tissue. Now researchers have trialed a technique designed to make low-grade gliomas visible. The technique involved using an innovative probe together with 5-ALA as a fluorescence marker during the operation.