Intraparenchymal subependymoma: Case report and literature review

Abstract

Background: Intracranial subependymomas are rare slow-growing benign tumors typically located in the ventricular system, accounting for 0.07-0.7% of all intracranial neoplasms. Intraparenchymal subependymoma is extremely rare lesions, imposing a challenging diagnosis and management.

Case description: We describe a case of a supratentorial intraparenchymal mass on left occipital lobe in a 26-year-old woman with progressive headache and visual impairment. Differential diagnosis mainly included gliomas, neuronal-glial tumors, ependymoma, and subependymoma. Complete surgical resection was performed and histopathology analysis confirmed diagnosis of subependymoma. Despite its benign behavior the Ki67/MIB-1 labeling index assessed by immunohistochemistry was 5%. After 1 year of follow-up she was free of tumor recurrence.

Conclusion: Intraparenchymal subependymoma is extremely rare tumors and literature review showed only 11 cases reported. In general, they are misdiagnosed as other tumors, so careful attention on clinical and radiological features must be taken when looking at a tumor close to the ventricular system, even though it does not have any obvious direct connection to it. Despite its benign nature, total removal must be attempted given that there are reports of recurrence, especially in partially removed tumors with high proliferation index. The role of adjuvant therapy is still limited and new treatment options are being developed as our knowledge on biological and molecular characteristics advances.

Keywords: Atypical; Intraparenchymal; Recurrence; Subependymoma.

Figure 1:

Imaging features of intraparenchymal subependymoma. (a) Axial gadolinium T1-weighted image showing a hypointense mass on the left occipital lobe, with mild contrast enhancement. (b) Axial T2 sequence showing a hyperintense heterogeneous mass. (c) Axial FLAIR sequence with hyperintense evident signal. (d) Axial diffusion-weighted sequence, with no diffusion restriction. (e) Axial ADC with increased signal compared to brain parenchyma. (f) Axial susceptibility weighted imaging showing small dots with hypointense signal within the lesion.

Figure 2:

Intraoperative images. (a) A 4 cm corticectomy was made and a soft, smooth-contoured, and lobulated mass was evident. (b) At the final steps of the resection it was possible to see the tumor corridor connected the walls of the ventricular system, choroid plexus (white asterisk) and the atrium of the left lateral ventricle (white arrow). (c) Ventricular drainage was placed under direct view for better managing the postoperative care. (d) Use of navigation to confirm the extent of the resection and confirming positioning of ventricular drainage.

Figure 3:

Imaging of postoperative MRI. (a) Day 1 after surgery axial gadolinium T1-weighted image showing no signs of contrast enhancement or presence of hypointense lesion previously visualized. (b) Day 1 after surgery axial T2 sequence without evidence of tumor. (c) Day 1 after surgery axial FLAIR sequence with slight hyperintense signal on tumor borders, compatible with recent postoperative imaging and no evidence of residual tumor. (d) One year after surgery axial gadolinium T1-weighted image showing no signs of contrast enhancement or tumor recurrence. (e) One year after surgery axial T2 sequence without evidence of tumor recurrence. (f) One year after surgery axial FLAIR sequence without evidence of tumor recurrence and improvement on hyperintense signal on tumor borders.

Figure 4:

(a) Positivity for glial fibrillary acidic protein. (b) Negativity for epithelial membrane antigen. (c) Clusters of cellular proliferation embedded in dense fibrillar matrix and large acelular zones. (d) MIB-1 staining showing labeling index of 5%.