The incidence of primary epithelial cancer of the thyroid is 0.7 per 100,000 in males and 1.9 per 100,000 in females in the UK. Overall, the annual incidence of thyroid cancer is between 0.9 and 5.2 per 100,000 people, with a ratio of women to men of 2–3:1. Thyroid cancer is the most rapidly rising incident cancer in women and the second most rapidly rising incident cancer in men in the USA. Whether the papillary or follicular histology is favored is dependent on the amount of dietary iodine in a particular region. Papillary thyroid carcinoma (PTC) accounts for more than 50 % of cases in the UK and USA, the next most common type of thyroid cancer being follicular thyroid carcinoma (FTC). Less frequent types are medullary thyroid carcinomas (MTC), anaplastic (undifferentiated) carcinomas, Hürthle cell carcinomas, and squamous cell carcinomas. Other non-epithelial malignancies that may be observed in the thyroid include lymphomas and sarcomas, but these are rare.