Thyroid tumours

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 favoured is dependent on the amount of dietary iodine in a particular region. Papillary carcinoma (PTC) accounts for more than 50 per cent of cases in the UK and USA, the next most common type of thyroid cancer being follicular carcinoma (FTC). Less frequent types are medullary (MTC), anaplastic (undifferentiated), Hurthle cell and squamous cell carcinomas. Other non-epithelial malignancies that may be observed in the thyroid include lymphomas and sarcomas, but these are rare.

PTC of the thyroid

Genetic susceptibility to PTC can be seen in familial adenomatous polyposis syndrome (FAP), Cowden syndrome (CS), possibly Carney complex (CNC) and in a familial site-specific syndrome. These syndromes are described in detail in the next section. Thyroid cancers can be detected in 5–25 per cent of FAP patients. It should be noted that there is preliminary evidence that what is commonly referred to as “PTC” in FAP is not identical to classic PTC.