Ependymoma

Pathologic Quiz Case

A 48-year-old Hispanic woman with a history of uterine leiomyomas presented with low back pain and lower extremity radiculopathy. No focal motor deficits were present. Magnetic resonance imaging demonstrated an enhancing, 2 × 1-cm intradural mass at L2-L3. The patient was admitted for laminectomy and excision of the mass. A tumor originating at the filum terminale was completely excised. The patient did well postoperatively and was discharged. The tumor was sent for intraoperative consultation. Grossly, the tumor measured 1.8 cm in length and ranged from 1.0 to 0.3 cm in diameter (Figure 1). The tumor was tan-white to tan-pink and focally hemorrhagic. Squash preparations demonstrated a papillary tumor composed of rosettelike structures surrounding a mucoid area with central vessels. This architecture was confirmed on frozen and permanent sections (Figure 2).

What is your diagnosis?

Pathologic Diagnosis: Myxopapillary Ependymoma

First described by Kernohan in 1932, myxopapillary ependymoma is a neoplasm that most often occurs in the lumbosacral area, particularly the filum terminale, and may present clinically as low back pain. Other reported locations include the lateral ventricle and the subcutaneous sacrococcygeal area. The male-female ratio of this tumor is 2.2:1, with a mean patient age of 36.4 years.1 Grossly, the tumor may be either encapsulated and easily re sected or adherent to the surrounding tissue and difficult to resect completely.2

Histologically, myxopapillary ependymoma is distinct. It consists of papillary arrangements of well-differentiated cuboidal to low columnar cells, which surround a central core of hyaline acellular connective tissue. The core may stain positively for mucin. The core contains centrally located small blood vessels.1 Anaplasia, mitotic figures, necrotic foci, and vascular overgrowth are usually absent.4 The tumor cells most often react positively for vimentin and glial fibrillary acidic protein. Also, 50% of cases have been reported to be positive for S100 proteins The cells are negative for cytokeratin.1

Ultrastructurally, myxopapillary ependymoma is similar to choroid plexus, with cells that may contain nonciliated intracytoplasmic lumens6 or abnormal arrays of microtubules. No specific molecular alterations have been reported, although some cases have had unusual features. One case was reported to contain a partial deletion of the short arm of chromosome 1. A second case, which occurred in the subcutaneous sacrococcygeal area, contained dicentric chromosomes and deletion of 11q.1

The chief differential diagnosis of myxopapillary ependymoma is a spinal paraganglioma. Paragangliomas may manifest a pseudopapillary pattern with mucoid vascular change, which can cause diagnostic difficulty. However, paragangliomas have cells that are more uniform and epithelial and sit squarely on capillary walls. These lack the loose and sweeping pattern of myxopapillary ependymomas. Also, paraganglioma cells have a distinct salt-and-pepper chromatin pattern. They react positively for chromogranin and are negative for glial fibrillary acidic protein.7 The histologie differential diagnosis also includes chordoma, myxoid chondrosarcoma, mesothelioma, and papillary adenocarcinoma,1 although these are generally excluded clinically and radiologically. The clinical differential diagnosis includes schwannoma and meningioma, which are easily excluded histologically.

The prognosis of this tumor is good, with curability more dependent on resectability than histologie features.8 Myxopapillary epenclymoma is ranked as a grade 1 tumor in the World Health Organization classification system.1 The course is much more favorable in easily and completely resected circumscribed tumors.8 Local recurrence occurs in incompletely resected tumors with death following a history of multiple local recurrences.2 Intracranial metastasis may also occur but is rare.2 Histologic criteria used to diagnose anaplasia in gliomas is unreliable for myxopapillary ependymomas. However, the mitotic count is significant for supratentorial cases.9

References

1. Kleihues P, Cavenee WK, eds. Pathology and Genetics of Tumours of the Nervous System. Lyon, France: IARC Press; 2000:78-79. World Health Organization Classification ot Tumours; vol 1.

2. Sonneland PR, Scheithauer BW, Onofrio BM. Myxopapillary ependymoma: a clinicopathologic and immunocytochemical study of 77 cases. Cancer. 1985;56:883-893.

3. Rawlinson DC, Herman MM, Rubinstein LJ. The fine structure of a myxopapillary ependymoma of the filum terminale. Acta Ncuropatho! (Berl) 1973;25:1-13.

4. Davis C, Barnard RO. Malignant behavior of myxopapillary ependymoma: report of three cases. J Neurosurg. 1985;62:925-929.

5. Coffin CM, Swamson PE, Wick MR, Dehner LP. An immunohistochemkal comparison of chordoma with renal cell carcinoma, colorectal adenocarcinoma, and myxopapillary ependymoma: a potential diagnostic dilemma in the diminutive biopsy. Mod Pathol. 1993;6:531-538.

6. Ho KL, Caccamo DV, Garcia JH. lntracytoplasmic lumina in ependymomas: an ultrastructure study. Ultrastruct Pathol. 1994;18:371-380.

7. Burger PC, Scheithauer BW. Tumors ot the Central Nervous System. Washington, DC: Armed Forces Institute of Pathology; 1994. Atlas of Tumor Pathology; 3rd series, fascicle 10.

8. Ross DA, McKeever PE, Sandier HM, Muraszko KM. Myxopapillary ependymoma: results of nucleolar organizing region staining. Cancer. 1993;71:3114-3118.

9. Schiffer D, Chio A, Giordana MT, et al. Histologie prognostic factors in ependymoma. Childs Nerv Syst. 1991;7:177-182.

Stephen M. Berns, MD; Marzena Wiacek, MD; Gary S. Pearl, MD, PhD

Accepted for publication February 26, 2004.

From the Department of Pathology, Orlando Regional Health Care, Orlando, Fla.

The authors have no relevant financial interest in the products or companies described in this article.

Corresponding author: Stephen M. Berns, MD, Department of Pathology, Orlando Regional Health Care, 1414 Kuhl Ave, Orlando, FL 32806 (e-mail: stephenmberns@aol.com).

Reprints not available from the authors.

Copyright College of American Pathologists Jul 2004
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