Extraspinal ependymomas have been described in the subcutaneous sacrococcygeal and presacral areas. Since 1984, eight pelvic ependymomas have been reported that have originated in the ovary, broad ligament, mesovarium, and omenturn. This report documents an additional case arising from the right uterosacral ligament in a 48-year-old woman. The diagnosis of ependymoma was supported by a histologic pattern of true rosettes and pseudo-rosettes, glial fibrillary acidic protein (GFAP) positivity, and electron microscopic findings of cilia, blepharoplasts, and intermediate filaments. The tumor was positive for cytokeratin and vimentin. Ultrastructurally, neurosecretory granules were present within the cytoplasm. These features have not been described previously in pelvic ependymomas. These tumors, although easily confused with serous papillary carcinoma, should be distinguished from serous papillary carcinoma because of their apparently better prognosis and tendency for late recurrence.
Cancer 64:2565-2571, 1989.
PENDYMOMAS account for 5% of intracranial and E 16% of spinal tumors.' Extramedullary ependymomas are rare tumors; they occur most frequently in the subcutaneous sacrococcygeal area and the presacral space.2 An additional site of origin of the ependymoma, i.e., from pelvic structures, has been reported recently. Kleinman et af. provided the first complete description of the pelvic ependymoma with their report on three cases of ovarian ependym~ma.~ Since then, five additional case histories have been published with origins including the broad ligament: mesovarium,' and omenturn: Due to their papillary and tubular growth pattern, these tumors are often misdiagnosed as papillary serous carcinoma or, as in one case, malignant mesothelioma. We report an additional case arising from the right uterosacral ligament. It includes an extensive immuno-