CALCA and medullary thyroid gland carcinoma: TC develops from two cell types in the thyroid gland: >90% is derived from the follicular cells–epithelial cells, which are responsible for iodine uptake and thyroid hormone biosynthesis; 3–5% is derived from parafollicular cells, which are responsible for the biosynthesis and secretion of hormone calcitonin (known as MTC (medullary thyroid carcinomas)) [2,3].