The PTEN gene was originally identified by three independent groups using different methodologies: a representational difference analysis of tumours; a high-density scan of chromosome 10q in glioma cell lines and a screening of human cDNA libraries designed to detect protein phosphatases upregulated in response to transforming growth factor β (TGF-β) (Maehama et al, 2001). Here, PTEN is linked to central nervous system cancer.