PTEN (phosphatase and tensin homolog), also known as MMAC1 (mutated in multiple advanced cancers) or TEP1(TGFb-regulated and epithelial cell-enriched phosphatase), was first identified as a tumor suppressor gene in 1997 by three independent groups through mapping human homozygous deletion on chromosome 10q23 (Li et al. 1997; Steck et al. 1997; Li and Sun 1997). The gene discussed is PTEN; the disease is neoplasm.