The authors report a case of clear cell ependymoma with a lipidized component that developed in the thoracic spinal cord. A 59-year-old man was admitted to the hospital with an itchy pain in the left forearm to the left anterior and lateral chest for the past three years. Neurological findings on admission included dissociated sensory disturbance below the C8 level and increased deep tendon reflex in both lower extremities. An MRI scan of the spinal cord revealed an intramedullary tumor with a longer diameter of 3.5 cm at the T3-T4 level and a distended syrinx at the T2-T3 level. Surgery was performed after T1-T5 laminectomy. The gray, soft and well demarcated tumor was removed subtotally. Light microscopy revealed a portion where clear cells proliferated and a portion where foamy cells proliferated. In some tissue, there were a very few anuclear areas suggestive of a perivascular pseudorosette. Neither nuclear division nor necrosis was observed. lmmunohistochemically, the tumor cells were positive for glial fibrillary acidic protein (CFAP), epithelial membrane antigen (EMA), vimentin, and negative for cytokeratin, synaptophysin. The MIB-1 staining index was 0.25%. Based on these findings, diagnosis of clear cell ependymoma with a lipidized component was made. [Neurol Res 2003; 25: 324-328]

Keywords: Ependymoma; clear cell; lipidized cell; spinal cord; epithelial membrane antigen

INTRODUCTION

Clear cell ependymoma is a subtype of ependymoma that was advocated by Kawano et al.1,2 in 1989 and was added to the WHO Classification of Tumors of the Central Nervous System revised in 19933. It is characterized by most of the tumor tissue consisting of clear cells lacking typical histological findings of ependymoma. It mainly develops in the cerebrum and cerebellum, and the development in the spinal cord has been reported in only one case4. Ependymoma with foamy cells in its tissue is rare and was named lipidized ependymoma by Takahashi ef al.5 in 1998. The authors report a case of clear cell ependymoma with a lipidized component that developed in the thoracic spinal cord.

CASE REPORT

This 59-year-old man visited the hospital with an itchy pain in the left forearm to the left anterior and lateral chest for the past three years and was hospitalized for detailed examination on October 29, 2001. Neurological findings on admission included dissociated sensory disturbance below the C8 level and increased deep tendon reflex in both lower extremities. An MRI scan of the spinal cord revealed an intramedullary tumor with a longer diameter of 3.5 cm at the T3-T4 level and a distended syrinx at the T2-T3 level. The tumor was visualized as being isointense on T1-weighted images, hyperintense on T2-weighted images, and enhanced by intravenous injection of gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) (Figure 1). Operation was performed in the prone position after T1-T5 laminectomy under general anesthesia on November 6, 2001. The spinal evoked potential was monitored during the operation. The tumor was gray, soft, and well demarcated. A subtotal excision was made with some ill-demarcated portions caudal to the tumor remaining. Muscle strength of both legs temporarily decreased after surgery, but the patient is now able to walk by himself and all neurological symptoms have improved. Neither radiotherapy nor chemotherapy was performed post-operatively. Light microscopy revealed a portion where clear cells having a round nucleus and a bright cytoplasm proliferated densely and a portion where foamy cells proliferated densely (Figure 2A). In some tissue, there were a very few anuclear areas suggestive of a perivascular pseudorosette (Figure 2B). Neither nuclear division nor necrosis was observed, lmmunohistochemically, the tumor cells were positive for glial fibrillary acidic protein (GFAP) (Figure 2C), epithelial membrane antigen (EMA) (Figure 2D), vimentin, and negative for cytokeratin, synaptophysin. The MIB-1 staining index was 0.25%. Based on these findings, diagnosis of clear cell ependymoma with a lipidized component was made. No electron microscopic specimens have been prepared.

DISCUSSION

Clear cell ependymoma is a tumor mostly consisting of clear cells, and infrequently shows typical features of ependymoma. Its definite diagnosis should be made based on electron microscopic evidence of microvilli, cilia, junctional complexes and microrosettes, etc. However, even in a case in which no electron microscopic specimens have been prepared, diagnosis can be made based on light microscopic findings, if it is immunohistochemically positive for GFAP and EMA. In such a case, the presence of EMA-positive microvesicular and granular structures is important6,7. Hirato ef al.6 pointed out that these EMA-positive structures under light microscope were consistent with intracytoplasmic lumina containing microvilli and intercelullar microrosettes under electron microscope.

There are 24 case reports in the literature, of clear cell ependymoma1,2,4,6,8-13 : 15 men and nine women with an average age of 30 years (range: 2-64 years). The reported site of development is intracranial supratentorial in 14 cases, intracranial infratentorial in nine and spinal cord in one. It is interesting that all five cases aged less than 15 years occurr in the intracranial supratentorial space, which is contrary to the clinical experience that ependymoma in childhood often occurs in the infratentorial space. Occurrence in the spinal cord has been reported in only one case4 and is thought to be very rare. Since Min ef al.13 reported that the biological malignancy of clear cell ependymomas is the same as that of other ependymomas and varies with individual cases, and that the MIB-1 staining index is required for evaluation of malignancy. In our case, the index was 0.25% and suggested a benign tumor.

There have been rare cases of ependymoma having many foamy cells. Takahashi ef al.5 named these tumors lipidized ependymoma. These cases are characterized by the presence of GFAP-positive foamy cells. These cells were present in our case. The mechanism of lipid accumulation in these cells is conceivably associated with the degeneration process like that in pleomorphic xanthoastrocytomas.

CONCLUSION

The authors report a rare case of clear cell ependymoma with a lipidized component that developed in the thoracic spinal cord. The definite diagnosis of clear cell ependymoma should be made based on electron microscopic evidence. However, even in a case in which no electron microscopic specimens have been prepared, diagnosis can be made based on light microscopic findings if it is immunohistochemically positive for GFAP and EMA. In such a case, the presence of EMA-positive microvesicular and granular structures is important.

ACKNOWLEDGEMENTS

The authors thank Dr Nobuyuki Kawano (Sagamihara, Japan), Dr Hitoshi Takahashi (Niigata, Japan) and Yoichi Nakazato (Maebashi, Japan) for their diagnostic advice. This work is supported in part by a Grant-in-Aid for Scientific Research (C:13671454) from the Japan Society for the Promotion of Science.

REFERENCES

1 Kawano N, Yada K, Aihara M, Yagishita S. Oligodendroglioma-like cells (clear cells) in ependymoma. Acta Neuropathol 1983; 62: 141-144

2 Kawano N, Yada K, Yagishita S. Clear cell ependymoma: A histological variant with diagnostic implications. Virchows Arch A Pathol Anat Histopathol 1989; 415: 467-472

3 Kleihues P, Burger PC, Scheithauer BW. Ependymal tumours. In: Histological Typing of Tumours of the Central Nervous System: World Health Organization International Histological Classification of Tumors, 2nd edn, Berlin: Springer-Verlag, 1993: pp. 17-18

4 Akutsu H, Shibata Y, Okazaki M, Hyodo A, Matsumura A. lntramedullary clear cell ependymoma in the cervical spinal cord: Case report. Neurosurgery 2000; 47: 1434-1438

5 Takahashi H, Goto J, Emura I, Honma T, Hasegawa K, Uchiyama S. Lipidized (foamy) tumor cells in a spinal cord ependymoma with collagenous metaplasia. Acta Neuropathol 1998; 95: 421-425

6 Hirato J, Nakazato Y, lijima M, Yokoo H, Sasaki A, Yokota M, Ono N, Hirato M, lnoue H. An unusual variant of ependymoma with extensive tumor cell vacuolization. Acta Neuropathol 1997; 93: 310-316

7 Uematsu Y, Rojas-Corona RR, Llena JF, Hirano A. Distribution of epithelial membrane antigen in normal and neoplastic human ependyma. Acta Neuropathol 1989; 78: 325-328

8 Abe T, Wada A, Mochizuki Y, Hara T, Sawabe Y, Sugita M, Nakabayashi M, Sashida J, Kawamoto S, Nagata K, Shimizu S, Matsumoto K. Clear cell ependymoma: A case report. No To Shinkei 1998; 50: 432-436 (Jpn)

9 Cenacchi G, Giangaspero F, Cerasoli S, Manetto V, Martinelli GN. Ultrastructural characterization of oligodendroglial-like cells in central nervous system tumors. Ultrastruct Pathol 1996; 20: 537-547

10 Hayashi K, Tamura M, Shimozuru T, Kasamo S, Hirahara K, Kadota K, Asakura T. Extra-axial ependymoma: Case report. Neurol Med Chir 1994; 34: 295-299

11 Kakita A, Takahashi H, Fusejima T, Konno K, Nakazawa T, Aoki K, Tanaka R, lkuta F. Clear cell variants of intracranial tumors: Meningioma and ependymoma. Brain Tumor Pathol 1995; 12: 111-116

12 Kawano N, Yagishita S, Komatsu K, Suwa T, Oka H, Utsuki S, Fujii K. Cerebellar clear cell ependymoma mimicking hemangio-blastoma: Its clinical and pathological features. Surg Neurol 1999; 51: 281-288

13 Min KW, Scheithauer BW. Clear cell ependymoma: A mimic of oligodendroglioma: Clinicopathologic and ultrastructural considerations. Am J Surg Pathol 1997; 21: 820-826

Yeong-Jin Kim*, Shigeru Tsunoda[double dagger] Kazuhiro Yokoyama*, Kazunori Miyamoto*, Masamitsu Tamai[dagger] and Michiko Yamauchi[dagger]

*Department of Neurosurgery, [dagger]Department of Pathology, Higashiosaka City General Hospital, Osaka [double dagger]Graduate School of Science, Osaka Prefecture University, Sakai, Japan

Correspondence and reprint requests to: Yeong-Jin Kim, MD, Department of Neurosurgery, Higashiosaka City General Hospital, 3-4-5 Nishiiwata-cho, Higashiosaka 578-8588, Japan, [y-kim@oph.gr.jp] Accepted for publication February 2003.

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