ABSTRACT
Background Thyroid cancer (TC) is a generic term for cancer arising in the thyroid gland.
More than 90% of TC originates from the follicular cells, whose task it is to produce thyroid hormone. Follicularcell-derived tumors are: (1) differentiated thyroid carcinoma (DTC; ~90%), which includes the papillary (PTC; ~80%) and the follicular (FTC; ~10%) subtypes, and (2) dedifferentiated, so-called anaplastic thyroid carcinoma (ATC; ~5%). C-cell carcinoma or medullary thyroid carcinoma (MTC) is derived from the calcitonin-producing C-cells and constitutes 5% of all cases of TC. MTC is distinguished from DTC by the absence of iodide uptake, the production of calcitonin as a tumor marker, and its frequent association with multiple endocrine neoplasia type II. Because of many special aspects in the management of MTC, including genetic testing, it will not be discussed in the present chapter.
