Oligodendrogliomas: impact of molecular genetics on treatment

The interest in oligodendrogliomas has increased since it became evident that a subset of these tumors respond to chemotherapy or radiation. This interest was augmented when the combined loss of the short arm of chromosome 1 and the long arm of chromosome 19 was identified as a powerful prediction factor for response. Lack of stringent morphological criteria allow high-interobserver variation with regard to classification and grading of oligodendroglial tumors. The prospect of beneficial chemotherapy prompted neuropathologists to diagnose more 'oligodendroglioma' than before. Therefore, there is great demand for unambiguous classification of oligodendroglial tumors. Supplementary analysis of the integrity of chromosomal arms 1p and 19q may greatly assist diagnostic characterization of tumors with oligodendroglial phenotype. The underlying mechanisms for these deletions are not known. Tumor suppressor genes on 1p and 19q relevant for oligodendroglioma have not yet been identified. Knowledge of these genes and the mechanisms of their inactivation might help to understand why oligodendroglial tumors do respond better to chemotherapy and radiotherapy than astrocytomas. This review compiles clinical, pathological and molecular genetic findings on oligodendrogliomas and oligoastrocytomas of WHO Grades II and III to present a brief overview on recent developments.