Oculomotor nerve teratoma

The case of a rare, mature teratoma of the oculomotor nerve manifesting as an interpeduncular cistern mass is presented. A basilar tip aneurysm initia lly was suspected on the basis of lesion location and MR imaging appearance . Subsequent CT and catheter angiography studies were atypical for aneurysm , leading to surgical biopsy. Pathologic analysis revealed a well-circumscr ibed mass composed of mature representatives of all three major cell tines characteristic of mature teratoma. The imaging findings are described, and a brief literature review is provided.