Molecular diagnostics of brain tumors – an up-date

In recent years there have been major advancements in the understanding of molecular events driving brain tumor genesis and progression. Although state-of-the-art techniques are not widely available, many of the molecular discoveries lead to novel antibodies that can assist in identifying the major molecular subgroups by immunohistochemistry. Molecular informations will likely be incorporated into the next World Health Organization (WHO) classifi cation of central nervous system tumors, but clinical practice in many centres have already taken on the available informations and therapeutic decisions are made based on genetic/epigenetic information. In the adult population IDH, ATRX and 1p/19q codeletion studies help to defi ne molecular subgroups that correlate better with prognosis and therapeutic response than traditional histology based diagnosis. The KIAA1549-BRAF fusion gene is a hallmark for pilocytic astrocytomas, while diffuse pediatric gliomas lack the IDH mutations and 1p/19q codeletions that are common in adult astrocytomas and oligodendrogliomas. Uncommon in adults, Histone H3.3 mutations are pathognomic in pediatric brainstem malignant gliomas. Molecular subgroups of medulloblastomas have also been identifi ed, and a corresponding set of antibodies are ready to guide treatment decisions in those centres where molecular techniques are not available. These genetic and epigenetic events determine a tumor’s behaviour, and integrating this level of informations into neuropathology practice is essential to provide the best possible care to both pediatric and adult patients.