Several groups have reported loss of heterozygosity, mutation or deletion of the gene in different cancers, including glioblastoma, prostate, lung and breast carcinoma and altered expression of PTEN was also detected in various precancerous lesions (Steck et al, 1997; Li et al, 1997b; McMenamin et al, 1999; Perren et al, 1999; Sano et al, 1999; Mutter et al, 2000). The gene discussed is PTEN; the disease is cancer.