As previously mentioned, despite the existence of more robust independent prognostic factors and advanced grading systems, such as the International MTC Grading System (IMTCGS) based on mitotic count, Ki67 proliferative index, and tumor necrosis, the most widely used biomarkers remain Ctn and CEA (54–57). This evidence concerns the gene MKI67 and medullary thyroid gland carcinoma.