Endodermal sinus tumor

Endodermal sinus tumor, abbreviated EST, is a member of the germ cell tumor group of cancers. It is also known as yolk sac tumor and as infantile embryonal carcinoma. It is the most common testicular tumor in children under three years old, and in this age group the outlook is very good. In infants the tumor tends to occur in its pure form, whereas in adults it is more often found mixed with other kinds of germ cell tumor, particularly teratoma and embryonal carcinoma. The mixture matters because a pure teratoma is usually benign, while the endodermal sinus tumor component is malignant. The condition therefore sits in the neoplasm chapter of disease classification and is discussed alongside the other germ cell tumors of the testis.