CALCA and medullary thyroid gland carcinoma: MTC was defined as an individual pathologic type of thyroid carcinoma (TC) in the late 1960s [2] based on the connection between the parafollicular or C-cells present within the thyroid cell population (originating in the neural crests and synthesizing the polypeptide hormone calcitonin), some particular morpho-functional characteristics, and the clinical course of malignant proliferation.