PTEN mutations have been implicated in variety of human cancers including endometrial cancer (30–50%) (Risinger et al, 1997; Tashiro et al, 1997), high-grade glioma (60–80%) (Louis and Gusella, 1995) and prostate cancer (29%) (Cairns et al, 1997), and homozygous deletion of the PTEN gene causes embryonic lethality (Podsypanina et al, 1999). The gene discussed is PTEN; the disease is central nervous system cancer.