American journal of human genetics
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PTEN, a protein tyrosine phosphatase with homology to tensin, is a tumor-suppressor gene on chromosome 10q23. Somatic mutations in PTEN occur in multiple tumors, most markedly glioblastomas. Germ-line mutations in PTEN are responsible for Cowden disease (CD), a rare autosomal dominant multiple-hamartoma syndrome. ⋯ Loss of PTEN expression was an early event, reflected in loss of the wild-type allele in DNA from normal tissue adjacent to the breast and thyroid tumors. In RNA from normal tissues from three families, mutant transcripts appeared unstable. Germ-line PTEN mutations predispose to breast cancer in association with CD, although the signs of CD may be subtle.