The pathological diagnosis of diffuse gliomas: towards a smart synthesis of microscopic and molecular information in a multidisciplinary context

Gliomas form a heterogeneous group of tumours of the central nervous system. Most gliomas, the so-called 'diffuse gliomas', are characterized by diffuse infiltrative growth in the neuropil. Based on histopathological analysis, diffuse gliomas are subdivided in astrocytic, oligodendroglial, and oligoastrocytic tumours and graded as WHO grade II (low grade), WHO grade III (anaplastic), or WHO grade IV (glioblastoma). Accurate distinction between the different diffuse glioma types and malignancy grades has significant prognostic and therapeutic implications. This review describes essential aspects of the microscopic diagnosis of diffuse gliomas. Because of problems with tissue sampling and imprecise criteria for typing and grading, unequivocal histopathological classification of diffuse gliomas can be challenging. The addition of molecular parameters contributes to a more objective pathological diagnosis of diffuse gliomas. A multidisciplinary approach is mandatory for achieving an optimal diagnosis for patients with these tumours.