OBJECTIVETo investigate the origin of mixed germ cell tumors in the pineal region based on the image data, surgical findings and pathological examination of the tumor.

METHODSThe preoperative CT and magnetic resonance imaging (MRI) findings and tumor specimens were retrospectively analyzed in 15 cases of pineal mixed germ cell tumors confirmed by postoperative histological examination between January 2000 and September 2010.

RESULTSRadiographic examination of the tumor revealed calcification in 12 cases, cystic changes in 10 cases, and the presence of lipid in 5 cases. On the anteroposterior images, the tumors appeared round or elliptic with smooth edge in 6 cases, and showed irregular shape with multiple processes on the edge in 9 cases. Surgical exploration found all the tumors located in the the suprapineal recess enclosed by the arachnoidal envelope of the Galen vein. Pathologically, 13 specimens contained germinoma component, 9 contained teratoma component, 4 had embryonic carcinoma component, 3 had choriocarcinoma component, 7 showed yolk sac tumor component, and 3 showed rhabdomyoma component. Germinoma components were found on the tumor margin in 7 specimens, and intermingled germinoma and other components were found in 10 specimens.

CONCLUSIONPineal mixed germ cell tumor originates from the residue germ cells around the pineal gland, and most likely evolves from single primordial germ cells.