Update on molecular and genetic alterations in adult medulloblastoma

Medulloblastoma encompasses a group of aggressively growing cancers that arise either in the cerebellum or brain stem. They present primarily in children, with 80-85 % of medulloblastomas being diagnosed in patients of 16 years and younger. In adults, medulloblastomas are rare and account for less than 1 % of intracranial malignancies. Due to the low incidence of medulloblastoma in adults, the biology and genetics of adult medulloblastomas have long been poorly understood. Many centers therefore still treat adults either by radiotherapy only or by using glioblastoma protocols (both often noncurative), or with standard pediatric medulloblastoma regimes (often associated with dose-limiting toxicity).Current clinical staging systems discriminate between standard-risk or high-risk patients based on clinical and histological parameters. However, clinico-pathological features often fail to accurately predict treatment response. In children, molecularly defined risk assessment has become important to improve survival of high-risk patients and to decrease treatment-related toxicity and long-term sequelae in standard-risk patients. However, several recent studies have shown that adult and pediatric medulloblastomas are genetically distinct and may require different algorithms for molecular risk stratification. Moreover, four subtypes of medulloblastoma have been identified that appear at different frequencies in children and adults and that have a different prognostic impact depending on age. Molecular markers such as chromosome 10q and chromosome 17 statuses can be used for molecular risk stratification of adult medulloblastoma, but only in a subgroup-specific context. Here we present an overview of the current knowledge of the genomics of adult medulloblastoma and how these tumors differ from their pediatric counterparts.