It is caused by inactivating mutations in the PTEN gene, a dual-specificity phosphatase that negatively regulates PI3 Kinase/AKT pathway; mutations in this gene have been detected in 5% of FTCs [22]; however, a mouse harboring a deletion of Pten in the thyroid developed thyroid hyperplasia and not FTC [23]. This evidence concerns the gene PTEN and thyroid cancer, nonmedullary, 2.