The objectives of this study were as follows: (i) analysis of genetic alterations with emphasis on RET fusion genes in a large series of local malignant and benign thyroid diseases, (ii) characterization of RET fusion-positive cases based on clinical and pathological data, and (iii) evaluation of long-term follow-up of patients with RET fusion-positive thyroid carcinoma. This evidence concerns the gene RET and thyroid gland carcinoma.