Subpial Cervical Subependymoma: Report of an Unusual Tumor with Review of Literature

Abstract

Subependymoma is rare benign neoplasm (World Health Organization Grade I) usually found in the 4^th ventricle and lateral ventricles. They were first described by Boykin as a separate entity in 1954. Subependymoma constitutes only 1%-2% of spinal ependymal tumors. Majority of the spinal subependymoma is intramedullary, with a rare few reported in the extramedullary plane. Clinicoradiologically, subependymoma often mimic more frequent, aggressive tumors of the spine (astrocytoma and ependymoma) which makes them difficult to differentiate. In fact, the diagnosis of subependymoma comes as a histopathological surprise. Maximal safe resection holds the key to good postoperative outcome with a very limited role of adjuvant therapy. Complete excision of the tumor, though desirable, is not feasible in all cases. Owing to their rarity and lack of characteristic clinicoradiological features, there is limited information currently available regarding their preoperative diagnosis and "optimal" management strategy. In this case report, we are discussing a case of eccentric subpial cervical subependymoma discussing important differentiating radiological features, and surgical nuances with an attempt to define "optimal" management strategy.

Keywords: Bamboo leaf sign; cervical; subependymoma; subpial.

Figure 1

The typical radiological findings in spinal subependymoma. A well-defined eccentrically placed, intramedullary lesion can be seen extending from cervicomedullary junction to C5 causing distinctive steep dilation of spinal cord: Bamboo leaf sign. Lesion is iso to hypointense on T1-weighted images (a and b) and hyperintense on T2-weighted image. There is no evidence of perilesional edema or syrinx formation (c). No significant enhancement is seen on T1-weighted postcontrast image (d and e)

Figure 2

(a) Microphotograph showing tumor composed of loose aggregates of cells with intervening hypocellular fibrillary matrix (H and E, ×10), (b) Immunohistochemistry showing expression of glial fibrillary acidic protein (IHC, ×20), (c) Immunohistochemistry shows expression of S-100 (IHC, ×20), and (d) Ki-67 proliferation index showing nuclear positivity in <1% cells (IHC, ×20)