Thyroid cancer accounts for 90% of all endocrine malignancies. A majority of thyroid cancers derive from follicular cells, with papillary thyroid carcinoma (PTC) being the most common type overall, followed by follicular thyroid carcinoma (FTC). The most common known cause of thyroid cancer is exposure to radiation. However, medullary thyroid carcinoma (MTC) can also develop in association with familial cancer syndromes, in particular multiple endocrine neoplasia (MEN). A number of specific genetic alterations have been identified in thyroid cancer. In particular, two molecular subtypes of PTC can be distinguished based on their mutation profile: BRAF-like PTC and RAS-like PTC, offering hope for targeted therapies. Most thyroid cancers have excellent prognosis, except for anaplastic thyroid carcinoma (ATC) which is a highly aggressive tumor associated with a nearly 100% mortality. It is hypothesized that it develops from well-differentiated follicular tumors (PTC or FTC) through accumulation of genetic alterations. The key to proper decision-making in patient management is differentiating between benign thyroid nodules which are very common and the nodules with a malignant potential. A number of diagnostic biomarkers (imaging, biochemical, and molecular) have been developed to this effect. In case of a confirmed thyroid malignancy, surgery is always the first treatment choice. Subsequent radioactive iodine treatment which may be accompanied by thyroxine administration is recommended for intermediate- and high-risk patients. Relapsing and metastatic disease which is refractory to those combined treatments, may respond to tyrosine kinase inhibitors or—in case of BRAF-mutant tumors—to selective BRAF inhibitors.