A 2-year-old boy is brought to the physician because his parents noticed a mass on his right testicle. Physical examination confirms the parents' observation. An orchiectomy is performed. Microscopic examination of the surgical specimen shows neoplastic cells forming glomeruloid Schiller-Duval bodies. Which of the following serum markers is most useful for monitoring the recurrence of tumor in this patient?

Most testicular neoplasms in the first 4 years of life are classified as yolk sac tumors. Microscopic examination of a yolk sac tumor shows interlacing strands of epithelial cells surrounded by loose connective stroma. The lobular arrangement of cells, surrounded by empty spaces, leads to the formation of glomeruloid structures referred to as Schiller-Duval bodies. Although yolk sac tumors are malignant, timely orchiectomy results in a 95% cure rate. These tumors produce a -fetoprotein, which can be used for monitoring the recurrence of disease following surgery Human chorionic gonadotropin (choice E) is secreted by choriocarcinoma.Diagnosis: Yolk sac tumor