Strategies that have been used to risk-stratify patients with sporadic MTC include segregating the tumors using the levels of Ctn and/or other markers, such as CEA, procalcitonin, pro-gastrin-releasing peptide, and carbohydrate antigen 19.9 (CA 19.9) [53,71]. The gene discussed is GRP; the disease is medullary thyroid gland carcinoma.