Differentiated thyroid cancer associated with intestinal polyposis syndromes: a review.

Intestinal polyposis syndromes, such as familial adenomatous polyposis (FAP) and Cowden's syndrome, are often associated with extraintestinal manifestations, and while many of these manifestations are benign, malignant extraintestinal manifestations, such as differentiated thyroid cancers, do occur. Although differentiated thyroid cancers (ie, papillary and follicular thyroid carcinomas) are associated with multiple syndromes, they are most commonly associated with intestinal polyposis syndromes. In the general population, the probability of developing thyroid cancer by age 65 years is only .5%. However, 1% to 2% of patients with FAP develop papillary thyroid carcinoma, the most common extraintestinal malignancy in patients with FAP. Also, up to 10% of patients with Cowden's syndrome will develop follicular thyroid carcinoma. The purpose of this review was to provide an overview of FAP, Cowden's syndrome, and Peutz-Jeghers syndrome, to discuss in detail the associations between intestinal polyposis syndromes and differentiated thyroid cancers, and to provide suggestions for screening and managing these diseases.