PTEN and thyroid cancer: Interestingly, Akt has been found to be activated by a genetic loss of expression of phosphatase and tensin homologue deleted on chromosome ten (PTEN), a tumour-suppressor gene, in Cowden's syndrome, an autosomal dominant multi-organ hamartoma syndrome characterised by benign and malignant thyroid tumours and breast and colon cancers (Dahia et al, 1997; Liaw et al, 1997).