Medulloblastoma: developmental mechanisms out of control.

Medulloblastoma, which is a highly aggressive central nervous system neoplasm, represents an intriguing example of how deregulated developmental mechanisms can lead to tumour development. Recent advances in the understanding of the role of Sonic Hedgehog, Wnt and Notch signalling pathways in the development of the cerebellum have shed new light on medulloblastoma pathogenesis.