Cowden syndrome is a hereditary condition which causes multiple types of benign tissue overgrowth (called hamartomas) and a risk of breast, thyroid, and uterine cancers. The most consistent features of CS are small flesh-colored bumps on the skin involving a hair follicle (trichilemmomas) and small wart-like growths (papillomatous papules) on the face, hands and mouth. CS is also often associated with a large head size (macrocephaly) and hamartomatous polyps of the small and large intestine. Thyroid adenomas, goiter, and nodules are also seen at increased frequency. Women are at increased risk for benign breast conditions, such as ductal hyperplasia, papillomatosis, fibrocystic breast disease, or fibroadenomas. Less commonly seen are benign fatty tumors (lipomas), blood vessel growths (hemangiomas), and other changes.
The breast, thyroid and uterus are the most common sites for cancer development in CS. About 30-50 percent of women with CS will develop breast cancer, often at a much younger age than average. This is compared to a risk of about 12 percent for women without CS. It is also common for women with CS to eventually develop cancer in both breasts. Only two men with CS have been reported with breast cancer, so it is not clear if men with CS have an increased risk for developing breast cancer. Studies have suggested that uterine (endometrial) cancer is also increased in CS, with a risk currently estimated at six to eight percent (compared to about 2.5 percent in women with average risk). Men and women with CS have about a three to 10 percent lifetime risk for developing thyroid cancer (compared to one percent for an average risk person). Recent data suggests that the risk for colon cancer may also be increased. Cancers of the skin, kidney, small bowel and others have been reported, but it is has not been proven if the risks for these cancers are increased for people with CS.
Although it is not certain at what age the features of Cowden syndrome begin to appear, we believe that more than 90 percent of people with CS have some features by the age of 20. However, people diagnosed with CS do not necessarily have all the same features. For example, most individuals with CS have some skin feature, up to 75 percent have a breast-related problem, and about 80 percent have a large head (macrocephaly), but they may have only some or none of the other features. Table 1 lists the features that have been associated with Cowden syndrome and the approximate percentage of people that develop each feature (incidence).