PTEN and thyroid gland undifferentiated (anaplastic) carcinoma: PTEN is downregulated in ~37% of well-differentiated thyroid carcinomas and downregulated or lost in >50% of highly malignant thyroid cancers [69]; point mutations or copy number changes in PIK3CA are found in ~23% of anaplastic thyroid cancers where they can coexist with either RAS or BRAF mutations [70].