Cowen syndrome is an inherited disorder characterized by multiple tumor-like growths called hamartomas and an increased risk of certain forms of cancer. Almost everyone with this condition has hamartomas. These small, noncancerous growths are most commonly found on the skin and mucous membranes (such as the lining of the mouth and nose), but can also occur in the intestinal tract and other parts of the body. People with Cowden syndrome have an increased risk of developing several types of cancer, including cancers of the breast, thyroid, and uterus. Indeed, women with Cowden syndrome have as much as a 25-50% lifetime risk of developing breast cancer. (Robbins & Cotran (2004). Pathological Basis of Disease, 7th Edition. Elsevier, 1134. ) Noncancerous breast and thyroid diseases are also common. Other signs and symptoms of Cowden syndrome can include an enlarged head, a rare noncancerous brain tumor called Lhermitte-Duclos disease.