The authors describe a case of Cowden's syndrome in a female patient with classic cutaneous lesions, plus papillomatous lesions in the gastrointestinal tract and a previous history of thyroid carcinoma. Mucocutaneous lesions occur in 90% of Cowden's syndrome cases and are characterized by facial trichilemmomas, oral mucosal papillomas and benign acral keratoses. Sites of extracutaneous involvement include: the thyroid, gastrointestinal tract, breast and endometrial tissue. There is risk of malignancies in these organs and they need to be monitored with imaging tests. The early diagnosis of the syndrome by a dermatologist through mucocutaneous lesions enables the investigation and diagnosis of extracutaneous involvement.