Ultrasound and magnetic resonance images of endodermal sinus tumor.

Endodermal sinus tumor, also known as yolk sac tumor, is a rare malignant ovarian tumor that usually occurs in the second decade of life. Here, we report a case of endodermal sinus tumor which occurred in a 14-year-old girl. She presented with lower abdominal pain for about 4 months. Initial ultrasound findings revealed a large ovarian multilocular solid tumor. Doppler study revealed multiple arteriole vessels running in the solid section of the tumor from which the lowest resistance index of 0.30 was recorded. The lactate dehydrogenase level was 261 U/L, and alpha-fetoprotein marker was 131,630 ng/mL. Axial contrast-enhanced T1-weighted magnetic resonance imaging showed a large cystic mass with solid components in the peripheral portions of the mass. The peripheral solid portions showed strong enhancement, indicating their hypervascularity. She received staging operation for malignant ovarian tumor, and the pathology reports revealed ovarian malignance of endodermal sinus tumor with omental invasion, stage IIIc. This case report suggests that in an adolescent female with elevated alpha-fetoprotein, low resistance index in the tumor mass and hypervascularity on contrast-enhanced T1-weighted magnetic resonance image, the probability of an endodermal sinus tumor should be highly suspected preoperatively.