Testicular teratoma presenting as a transilluminating scrotal mass.

Prepubertal testicular neoplasms are uncommon and differ from adult neoplasms in histopathologic features and presentation. The presented case describes a 3-year-old boy with an enlarged, transilluminating scrotal mass. Ultrasonography revealed a heterogeneous mass and absence of a hydrocele. After right radical orchiectomy, pathologic examination confirmed the mass as a mature teratoma. Although tumor registries cite yolk sac tumor as the most common prepubertal testis neoplasm, more recent studies have demonstrated benign tumors such as teratomas to be more common. Although rare, some prepubertal tumors such as teratomas may transilluminate. Ultrasonography should be used to evaluate hydroceles when the testis is impalpable.