Cowden syndrome (also known as “Cowden’s disease,” and “Multiple hamartoma syndrome”) is a rare autosomal dominant inherited disorder characterized by multiple tumor-like growths called hamartomas and an increased risk of certain forms of cancer.

Cowden syndrome is associated with loss-of-function mutations in PTEN, a tumor suppressor gene, leading to hyperactivity of the mTOR pathway. These mutations lead to characteristic features including macrocephaly, intestinal hamartomatous polyps, benign skin tumors (multiple trichilemmomas, papillomatous papules, and acral keratoses) and dysplastic gangliocytoma of the cerebellum (Lhermitte-Duclos disease). In addition, there is a predisposition to breast carcinoma, follicular carcinoma of the thyroid, and endometrial carcinoma.