Parapharyngeal and skull base yolk sac tumor: a case report with lessons in diagnosis and management.

Yolk sac tumors are rare in the head and neck. A previously healthy 2-year-old female presented with a large parapharyngeal mass. Pathology was pathognomonic for yolk sac tumor, with glandular differentiation and focal mucin production, which has not been reported in a yolk sac tumor. She was treated aggressively with chemotherapy followed by endoscopic exploration with planned resection, but no viable tumor was encountered. Yolk sac tumors can be difficult to diagnose in the head and neck, but complete clinical response can be achieved. New endoscopic approaches to skull base tumors are applicable to the pediatric population with some technical modifications.