RET and differentiated thyroid carcinoma: In approximately 20% of human papillary thyroid carcinoma (PTC), RET exons encoding the tyrosine kinase domain are fused to the promoter region and the 5’-ter exons of heterologous genes, generating chimeric oncogenes, such as CCDC6-RET (RET/PTC1) or NCOA4-RET (RET/PTC3) [1, 2].