Yolk sac tumor

Yolk sac tumor (YST), also known as endodermal sinus tumor, is a rare malignant germ cell tumor that recapitulates the yolk sac structure of early embryonic development. It is the most common testicular tumor in children under 3 years of age and can also occur in the ovaries, as well as in extragonadal midline sites such as the mediastinum, sacrococcygeal region, and central nervous system. In females, ovarian yolk sac tumors typically present in adolescents and young adults. The tumor produces alpha-fetoprotein (AFP), which serves as an important serum biomarker for diagnosis, monitoring treatment response, and detecting recurrence. Clinically, yolk sac tumors present as rapidly growing masses. Testicular YST in young boys typically manifests as a painless scrotal swelling, while ovarian YST in young women often presents with abdominal pain, a pelvic mass, and sometimes abdominal distension due to ascites. Extragonadal tumors present with symptoms related to their anatomical location. Histologically, the tumor is characterized by a reticular pattern with Schiller-Duval bodies, which are pathognomonic structures resembling glomeruli. The treatment landscape for yolk sac tumors has improved dramatically over recent decades. Management typically involves surgical resection combined with platinum-based chemotherapy, most commonly the BEP regimen (bleomycin, etoposide, and cisplatin). In pediatric testicular YST confined to the testis (stage I), radical inguinal orchiectomy followed by surveillance may be sufficient. For advanced-stage disease or ovarian YST, fertility-sparing surgery (unilateral salpingo-oophorectomy) combined with adjuvant chemotherapy is standard. With modern treatment protocols, cure rates are high, exceeding 90% for early-stage disease, though advanced or recurrent disease carries a less favorable prognosis. Serial AFP monitoring is essential during follow-up to detect relapse early.

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