We report a case of myxopapillary ependymoma presenting as a primary tumor of the subcutaneous tissue in the sacrococcygeal region. The mass was large, well-encapsulated, lobulated, and multiseptated, with varying signal intensity on T1- and T2-weighted MR images caused by hemorrhagic necrosis, blood degradation products, and calcification. Only a small viable portion enhanced after administration of contrast material. Multiple lobules formed from fibrous septa and dystrophic calcification also characterize this tumor.

Subcutaneous sacrococcygeal myxopapillary ependymoma.Med Pediatr Oncol. 1998 Feb;30(2):81-4.

We report an 8-year-old boy with a primary subcutaneous sacrococcygeal ependymoma, a rare tumor that is thought to arise in embryologic rests. The lesion was completely removed in our patient, who has been followed without recurrence for 20 months. Our experience, together with that of the other 15 cases in the world literature, supports surgical excision as the mainstay of treatment.

Extradural myxopapillary ependymoma: report of two cases and review of the literature.Pediatr Pathol Lab Med. 1996 Sep-Oct;16(5):813-22.

The cauda equina is the most frequent location for ependymomas, particularly the myxopapillary variant, which generally arises from the filum terminale. These tumors have a characteristic histopathologic pattern and are usually easily recognized. The occurrence of these tumors in an extradural, sacrococcygeal, or subcutaneous location may prove challenging, particularly in the absence of any obvious central nervous system connection. We describe two such extradural cases, one with multiple regional and distant metastases and the other with multiple recurrences. The origin of these tumors from subcutaneous sacrococcygeal ependymal rests is postulated on the basis of earlier reports. Clinical and histopathological features are described and a review of the literature is presented.