General
- Most common out of the three spinal cord ependymomas
- Slow growing variant of ependymoma
Definition
- Essential:
- Glioma with papillary structures and perivascular myxoid change or at least focal myxoid microcysts AND
- Immunoreactivity for GFAP AND
- (for unresolved lesions) DNA methylation profile aligned with myxopapillary ependymoma
- Desirable:
- Papillary arrangements of tumour cells around vascularized fibromyxoid cores
- Location in the filum terminale or conus medullaris
Numbers
- 10% of all ependymomas
- In the conus medullaris and cauda equina region: it’s the most common intramedullary neoplasm
- Median age at diagnosis was 33.5 years
- Male to female ratio of 2.2:1
Localisation
- Almost entirely confined to the lumbar spine and usually solitary.
- Conus medullaris
- Cauda equina
- Filum terminale
- These tumours may fill the entire lumbosacral spinal canal
- Rare
- Cervico-thoracic spinal cord
- Fourth ventricle
- Lateral ventricles
- Brain parenchyma
CNS WHO grading
- CNS WHO grade 2 rather than 1
- Since its likelihood of recurrence is now understood to be similar to conventional spinal ependymoma.
- But behaves aggressively (Recurrence and CSF dissemination) that usually translates to multiple surgeries in the patient’s lifetime
- May have a more aggressive variant in children
- Paediatric patients are at increased risk of dissemination at the time of diagnosis, which is evident in over 50% of cases at the time of diagnosis
Clinical presentation
- Due to its unique location (in lumbar spine only), symptoms are usually attributable to dysfunction of the conus or cauda equina.
- Long duration back pain
Molecular pathology
- Identifiable by methylome studies but further molecular classification does not provide added clinicopathological utility
Origin
- Ependymal glia of filum terminale
- Subcutaneous sacrococcygeal or presacral myxopapillary ependymomas are a distinct subgroup but might have originate from the same cells and are ectopically distributed subcutaneously
Radiology
- Sharply circumscribed and contrast enhancing
- Can have cystic changes and haemorrhage
T1+C
T2
T1 Stir
Histopathology
- Macroscopic
- Scallop bone
- Erode through dura
- Become densely adherent to the nerve roots of the cauda equina
- Microscopic
- Well differentiated cuboidal to elongated tumor cells radially oriented around vascularized myxoid cores with a myxopapillary appearance
- Usually no atypia, no / low mitotic activity
- Immunostaining
- + GFAP, mucin (PAS or Alcian blue, including vessel walls), vimentin
- - Cytokeratin
Treatment
General
- EANO guidelines: Key recommendations for the treatment of MPEs WHO grade I
- Gross total resection is recommended whenever feasible.
- Postoperative MRI should be performed to evaluate the extent of resection.
- Because a risk of CSF dissemination exists for all newly diagnosed patients, disease staging, including both craniospinal MRI and CSF cytology, is recommended following surgery (not earlier than 2-3 wk).
- Postoperative radiotherapy with doses 250 Gy is recommended in case of incomplete resection.
- In case of relapse, consideration should be given to re-operation, re-irradiation, and chemotherapy.
- Because of the risk of asymptomatic and/or late relapses, patients should be followed long term with a MRI + C.
- For distant metastases (Kraetzig 2018)
- With clinical manifestation for surgery or craniospinal irradiation
- Without clinical manifestation for observation
Surgery
- Aim for gross total resection (GTR).
- Incidental, small, asymptomatic tumours may be operated on early as the chance of curative and complete excision is good at this stage reducing the risk of dissemination and progression to irresectability is reduced.
- Attempts should be made to remove tumors en bloc to avoid the risk of seeding.
- In practice, an en-bloc excision is sometimes difficult to achieve as the tumour capsule is thin and the tumour itself is usually soft.
- In patients with tumors at high risk of seeding, the craniospinal axis should be treated.
- Surgical techniques - Dr Frederick Boop
- Open the theca while keeping the arachnoid intact
- The arachnoid is clipped to the dura so that when closing the arachnoid can be closed with the dura as well.
- This is because the tumour is located and spreads within arachnoid spaces, therefore if you keep the tumour within the arachnoid space it can limit the spread
- Remove the tumour enbloc
- Disconnect it from the Filum as low down as possible and disconnect as close to the cord as possible with IOM.
RT
- Indication:
- Residual tumour (STR)
- Distant metastasis - craniospinal irradiation
Outcome
- Rarely invade nerve roots or erode sacral bone
- Gross total resection may be most predictive factor for outcome
- 5-year survival rate of 98.4% after total or partial resection
- Recurrence
- Mainly local
- Risk factor
- Higher in younger patients
- If not treated initially with adjuvant radiotherapy
- Expression of EGFR
- Zhang 2023 n=72 China
- 29.2% had preoperative spinal drop metastases
- 18.9% relapsed, and preoperative drop metastasis occurred in 58.3%
- PFS
- 5-year 82%
- 10-year 77%
- Good prognostic factor
- Improved PFS
- GTR was associated with improved PFS (hazard ratio [HR] 0.149, p=0.014)
- Adjuvant radiotherapy (RT) was significantly associated with improved PFS in patients with preoperative drop metastasis (p=0.039).
- Poor prognostic factor
- Tumour recurrence
- Preoperative drop metastasis (HR 3.648, p=0.027)
- Tumour involvement sacrococcygeal region (HR 7.563, p=0.003) were associated with tumour recurrence.
Differential diagnosis
- Carcinoma: keratin+, GFAP-
- Chordoma: cords and lobules of physaliphorous cells, keratin+, GFAP-
- Meningioma: mucin-, GFAP-
- Myxoid chondrosarcoma
- Paraganglioma: cells are more uniform and epithelial and rest on capillary walls, salt and pepper chromatin; secretory granules (EM), mucin-, GFAP-
- Schwannoma: mucin
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