Postchemotherapy retroperitoneal residual mass in infantile yolk sac tumor

Background: Persistent postchemotherapy retroperitoneal residual mass with normalization of alpha-fetoprotein (AFP) in infantile yolk sac tumor is rar e. Methods/Results: A 38-month-old boy with recurrent yolk sac tumor was treat ed with cisplatin-based combination chemotherapy. After chemotherapy, the r etroperitoneal lymph node metastasis, 7x6 cm in size, decreased to 2 x 2 cm . Serum AFP levels returned to normal. The retroperitoneal residual mass wa s resected and histologically showed complete necrosis without viable cance r cells. Conclusion: The patient has remained free of disease for 36 months after op eration.