Gliomas are derived from glial cells and are the most common type of primary brain tumors in adults. Gliomas are classified by the World Health Organization (WHO) according to their malignancy grade and histological and molecular features. Malignancy grades range from I to IV. WHO grade I tumors are benign tumors, mostly occurring in childhood. High-grade gliomas (WHO grades III and IV) are undifferentiated and fast-growing tumors, with glioblastoma being the most common and malignant form. Patients with glioblastomas have a median survival of only 15 months. Clinical outcomes vary, however, and markers are needed to assist in the decision-making process and management of these patients. PROX1 is a transcription factor critical for embryonic development, with a role in cell cycle control and progenitor cell differentiation. Apart from its role in normal central nervous system development, PROX1 has been ascribed both tumor suppressive and oncogenic roles in several human cancers. The role of PROX1 as a prognostic factor for survival in patients with glioblastomas was the focus of paper I.

Gliomas WHO grade II, also called diffuse low-grade gliomas (DLGGs), are well-differentiated tumors that occur mainly in adult life, with a peak incidence at around 30–35 years of age and a median survival of 5–10 years. DLGGs grow continuously at a rate of a few mm per year and have a strong tendency to infiltrate the white matter tracts surrounding the tumor. Eventually these tumors transform into high-grade gliomas, but, as is the case with glioblastomas, there is a large variety of clinical outcomes. For radiological diagnosis, magnetic resonance imaging (MRI) is routinely used, often in combination with advanced MRI. Positron emission tomography with amino acid tracers provides additional diagnostic accuracy. From a histological as well as imaging point of view, DLGGs are heterogeneous tumors. The heterogeneity of DLGGs, in particular the correlation between radiological and histological tumor features, was the focus of paper II & paper III.

Seizures are amongst the most common presenting symptoms of patients with gliomas. Seizure semiology in patients with brain tumors and other structural brain lesions is closely related to the anatomical location of the lesion and the involvement of functional networks. A possible dynamic interplay between the anatomical region of seizure onset and connected target areas within the network was the focus of paper IV.