Paracentric reversal with the fusion of the protooncogene RET and the gene H4/D10S170 or the gene RFG/ELE1 drives to the active way RET/PTC that codifies a protein with protein kinase activity in 50% of papillary thyroid cancers and also in benign nodules (29.2%), so this activation is not a marker of malignity. The gene discussed is RET; the disease is thyroid gland papillary carcinoma.