A 3-month-old boy is brought to the physician because his parents cannot find one of his testicles. Physical examination confirms the parents' observation. The patient develops a urogenital tumor 30 years later. An abdominal-pelvic CT scan reveals metastases to lumbar periaortic lymph nodes. Which of the following is the most likely pathologic diagnosis?

The clinical significance of undescended testes is not related to the abnormal position of the gonad (patients are asymptomatic) but to an increased incidence of infertility and germ cell neoplasia. All men with untreated bilateral cryptorchid testes have azoospermia and are infertile. Unilateral cryptorchidism is associated in 40% of cases with oligospermia. Cryptorchidism is associated with a 20- to 40-fold greater than normal risk for testicular cancer. Conversely, 10% of patients with germ cell neoplasia have cryptorchid testes. Seminoma is the most common germ cell malignancy. The other choices are not complications of cryptorchidism.Diagnosis: Seminoma