Abstract

Yolk sac tumor is a rare malignant germ cell tumor that occurs in both gonadal and extragonadal tissues. Its germinal origin was first recognized by Teilum who suggested the term "Endodermal sinus tumor" for this neoplasm. The most specific feature of this rare neoplasm is the blood vessels and peripheral sleeve of malignant embryonic epithelial cells with sinusoidal and papillary or gloineruloid pattern. We experienced 4 cases of yolk sac tumor, one of which is combined with dysgerminoma of ovary in a 25-year old women, 2 cases arises in the sacrococcygium, one case of testis in a 3-year old boy and one case occurred in the ovary in a 15-year old women. The demonstration of alpha-fetoprotein in the serum of patients were turned out as all positive and positive alpha-fetoprotein with yolk sac tumor lentos further support to the yolk sac origin of these tumors. The 4 cases are reported with review of the literature.