Cowden syndrome is an inherited disorder characterized by multiple noncancerous, tumor-like growths called hamartomas on various areas of the body. Affected individuals are at an increased risk of developing certain cancers, especially cancer of the breast, thyroid or endometrium (lining the uterus). Cowden syndrome is caused by mutations in the PTEN, SDHB, SDHD, and KLLN  genes. This condition is inherited in an autosomal dominant pattern. In some cases, an affected person inherits the mutation from one affected parent. Other cases may result from new mutations in the gene.