Cowden disease (also known as Cowden syndrome) is characterized by multiple organ hamartomatous tumors and an increased risk of malignancy, in particular of the breast, thyroid and endometrium. Testicular tumors including seminoma have previously been reported in adult patients. We are reporting, for the first time, a case of testicular mixed germ cell tumor in an adolescent with Cowden disease. An association of testicular malignancy in Cowden disease could be explained by the previous observation of strong PTEN gene expression in the basal cell layer around seminiferous tubules and increased frequency of PTEN mutations in cultured testicular cancer cell lines. Surveillance for breast, thyroid, endometrial and renal cancer has been recommended for individuals with Cowden disease. The association of Cowden disease and testicular malignancy in our case suggests the need for additional screening of testes.
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