Path Quiz Case4: Diagnosis-

August  2009

Normal Anatomy of the Nerve

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Myxopapillary ependymoma is a distinctive variant of ependymoma which was first described as a separate pathological entity by Kernohan JW (Primary tumours of the spinal cord and intradural filum terminale - Cytology and cellular pathology of the nervous system. Vol 3 , 1932: 993-1025).

These tumours are usually restricted to the conus medullaris and filum terminale.

Extraspinal (soft tissue) myxopapillary ependymomas are rare tumours  which occur as direct extension into the soft tissue of the sacrococcygeal area from a primary ependymoma of the spinal cord,  cauda equina or filum terminale. Alternatively these may occur as primary pre-sacral, pelvic or abdominal tumours or as  primary tumours of the skin and subcutaneous tissue without direct connection to the spinal cord or filum terminale.

These tumours originate from extramedullary ependymal rests representing remnants of the coccygeal medullary vestige , an ependyma lined cleft , and is a derivative of the caudal neural tube persisting beneath the skin of the postanal pit .

These slow growing tumours usually affect patients in the 3rd and 4th decades and are slightly more common in males.

Clinically, this lesion is often misdiagnosed as a  pilonidal sinus or cyst. The differential diagnosis also includes sacrococcygeal teratoma, neurogenic tumour, soft tissue sarcoma and metastatic carcinoma. When the tumour involves sacrum and coccyx , tumours such as chordoma and chondrosarcoma must also be excluded.

Macroscopically the tumour usually presents as a well circumscribed, encapsulated, ovoid mass. The cut surface has a greyish white, lobulated appearance . In some cases cut surface shows mucoid areas, together with areas of hemorrhage, calcification, fibrosis and  cystic changes.

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Myxopapillary ependymoma has a distinctive appearance consisting of cuboidal , columnar  and spindle cells separated by basophilic mucinous material and characteristic papillary arrangement around hyalinized blood vessels. 

Histologically the differential diagnosis includes chordoma and schwannoma. Immunopositivity of the tumour cells with GFAP helps in confirming the diagnosis of myxopapillary ependymoma.

These are indolent tumours and in most cases are completely curable following total surgical resection. Following incomplete removal of the tumour there is an increased risk of recurrence. The tumour has the potential to metastasize to the lung, liver and lymph node. Prolonged post operative follow up is necessary as late recurrences may occur several  years after the primary tumour is removed.