Description
Subependymoma is a slow-growing, benign neoplasm that arises from the subependymal glial cells of the central nervous system. This tumour typically occurs in the ventricles or spinal cord, and is categorised as a grade I neoplasm in the WHO classification of CNS tumours.
Pathogenesis
The pathogenesis of subependymoma is still poorly understood. These tumours originate from the subependymal glial cells which line the ventricles of the brain and the central canal of the spinal cord. The tumours grow slowly, rarely infiltrating the surrounding brain or spinal cord tissue.
Epidemiology, Risk Factors & Associations
- Mostly diagnosed in adults (median age: 40-60 years).
- No significant gender predilection.
- No known risk factors or associations.
Clinical Features
- Clinical presentation can vary, primarily dependent on the location of the tumour.
- In ventricular tumours, symptoms may be due to obstructive hydrocephalus.
- Spinal cord subependymomas can present with local pain, radiculopathy or myelopathy.
Complications
- Potential for obstructive hydrocephalus with intraventricular lesions.
- Neurological deficits due to spinal cord compression.
Pathological Features
Histopathology
- Macroscopic: Tumours are typically small, well-circumscribed, and greyish.
- Microscopic: Characterised by clusters of uniform, round-to-oval cells embedded within a dense, collagenous or myxoid matrix.
Serology
No specific serological markers.
Biochemistry
No specific biochemical markers.
Radiological Features
General Features
- Typically appears as an intraventricular or intraspinal mass that may cause ventricular obstruction or cord compression.
- Most common location is inferior fourth ventricle (50-60%), followed by frontal horns of lateral ventricles usually attached to the septum pellucidum (30-40%), third ventricle (rare) and central canal of the spinal cord (rare).
- Calcifications can be observed.
- Hydrocephalus may be observed.
CT
- Non-contrast: Iso- to hyperdense relative to brain parenchyma.
- Contrast-enhanced: Variable enhancement.
MRI
- T1WI: Usually homogenous solid mass which is isointense to hypointense compared to white matter. May be heterogenous in large lesions.
- T2WI: Isointense to hyperintense mass to brain parenchyma. Heterogeneity may relate to cystic change, blood products or calcifications (usually seen in larger lesions).
- T1 C+: Usually non-enhancing or diffusely mildly enhancing.
- FLAIR: No oedema is not usually seen in adjacent brain parenchyma.
- SWI/GRE: Blooming artefact from calcifications.
- DWI/ADC: No specific features.
PET FDG
Not typically performed for subependymomas.
Grading and Staging
- Graded as WHO Grade I, indicating a slow-growing, well-differentiated neoplasm.
- No specific staging system due to its benign nature.
Differential Diagnosis
- Ependymoma: More commonly seen in children and young adults. Typically has a more aggressive course and more pronounced enhancement on imaging.
- Central Neurocytoma: Primarily occurs in young adults. Characterised by a lateral ventricular mass attached to septum pellucidum with a ‘soap-bubble’ or ‘bubbly’ appearance. Demonstrates moderate to strong enhancement.
- Choroid Plexus Papilloma: Occurs predominantly in children. Typically arises from the choroid plexus, and presents as a well-defined, lobulated, contrast-enhancing mass.
Management
- Surgical resection is the treatment of choice.
- Adjuvant therapy is typically not required due to the benign nature of the tumour.