Starting from these observations, a group of internationally recognized experts in thyroid pathology from the USA, Europe, and Australia recently proposed the International Medullary Thyroid Carcinoma Grading System (IMTCGS) that, combining proliferation (mitotic count and Ki67 proliferative index) and necrosis, separates MTC in two different prognostic categories: low and high grade MTC (Fig. 3 and Table 2) [53]. The gene discussed is MKI67; the disease is thyroid gland carcinoma.