Lhermitte-Duclos disease associated with Cowden disease.

We encountered a patient with Lhermitte-Duclos disease accompanied by Cowden disease, the second reported in Japan. The histological findings are described in detail. It is important to suspect Cowden disease in patients with Lhermitte-Duclos disease. Although Cowden disease is little known, making the diagnosis is very important, because cancer frequently occurs in the patient's family and genetic counseling is necessary.