Primary Yolk Sac Tumor of the Endometrium with MRI Findings: A Case Report

Primary yolk sac tumor (YST) of the endometrium is a very rare malignant germ cell tumor, primary YST of the endometrium with detailed magnetic resonance imaging (MRI) and contrast-enhanced MRI (CE-MRI) findings have not yet been reported in the English literature. We report a 40-year-old woman presenting with irregular lower abdominal pain and dysmenorrhea for more than 5 months. MRI showed a lesion in the right side wall of the uterus. Postoperative pathology and immunohistochemistry confirmed the diagnosis of primary YST of the endometrium with the International Federation of Gynecology and Obstetrics (FIGO) system staging of IV. The signal of the tumor was complex and lacked specific characteristic. Diffusion-weighted imaging (DWI) showed that the lesion is diffuse limited, the average apparent diffusion coefficient (ADC) value of the solid component was 0.735 × 10-3 mm2/s. CE-MRI showed that the irregular lesions presented uneven and mild enhancement in the arterial stage, and continued to strengthen in the venous phase, and strengthened close to the myometrium in the delayed phase. Primary YST of the endometrium should be considered if MRI scans show an irregular lesion in the myometrium with high level of alpha-fetoprotein (AFP).