The molecular evolution of medulloblastoma is more complex than was previously imagined as emerging evidence suggests that multiples interactions between the tumor cells and components of the tumor microenvironment (TME) are important for tumor promotion and progression. The identification of several molecular networks within the TME, which interact with tumoral cells, has provided new clues to understand the tumorigenic roles of many TME components as well as potential therapeutic targets. In this review, we discuss the most recent studies regarding the roles of astrocytes in supporting the sonic hedgehog (SHH)–activated medulloblastoma molecular subgroup, and provide an overview of medulloblastoma progression through SHH expression and signal transduction mechanisms into the complex tumor microenvironment. In addition, we highlight the associations between tumor and stromal cells as possible prognostic markers and new therapeutic strategies.