Cowden syndrome (CS) is an autosomal dominant hereditary disorder caused by mutations in the phosphatase and tensin homolog (PTEN) gene, and it is estimated to occur at a frequency of 0.5 cases per 100000 population.1) CS is known to be associated with multiple hamartomas of the skin, mucous membranes, brain, breast, thyroid, and colon. The gene discussed is PTEN; the disease is Cowden disease.