In 1997, two groups independently searching for tumour suppressors on chromosome 10q23, a locus that is frequently deleted in a variety of human cancers [167], identified a new phosphatase termed PTEN (phosphatase and tensin homolog deleted on chromosome 10), also known as MMAC (mutated in multiple advanced cancers) [168] or TEP1 (transforming growth factor-β-regulated and epithelial-cell enriched phosphatase 1) [169]. The gene discussed is PTEN; the disease is neoplasm.