Dysplastic gangliocytoma (Lhermitte-Duclos disease) associated with Cowden disease: report of a case and review of the literature for the genetic relationship between the two diseases.

We report a case of dysplastic gangliocytoma of the cerebellum (Lhermitte-Duclos disease, LDD). The patient also had cutaneous and mucosal hamartomas, adenomatous goiter, bilateral breast tumors, and gastrointestinal polyposis, indicating the diagnosis of Cowden disease (CD), the familial hamartoma syndrome. This was a rare sporadic case without any family history of CD, though CD is considered to be an autosomal dominant hereditary disease. Based on a thorough review of the previously reported cases, it is reasonable to consider that CD is inherited in autosomal dominant fashion through a CD gene (PTEN) containing a germline mutation, and that the occurrence of LDD is predicted on an additional somatic hit on the remaining normal CD allele or another unknown gene.