However, researchers recently began to investigate NKX2.1 expression in human tumor tissues and found reduced NKX2.1 expression in some types of cancer, including lung cancer, thyroid cancer and ovarian carcinomas [10]–[17], which suggested that NKX2.1 may be a putative new tumor suppressor in multiple types of human cancers. This evidence concerns the gene NKX2-1 and thyroid cancer.