EPENDYMOMA

EPENDYMOMA

• Ependymoma is tumor consisting of cells showing ependymal differentiation. Ependymal cells line the fluid filled spaces of the brain (ventricles) and spinal cord

• They comprise 4% of all the CNS tumors in adults

• Molecular and cytogenetic findings

  • Genetic abnormalities in tumor differ upon the anatomical sites

  • Loss of chromosomal arm 22q was noted in both spinal cord and intracranial tumors

  • Most intracranial tumors shows 

    • Gain of 1q

    • Losses on 6q, 9 and 13

  • Spinal cord tumors shows 

    • Gain on chromosome 7

    • Frequent losses on 6q, 4q, 10 and 2q

  • Myxopapillary ependymomas shows 

    • Loss on 13q14-q31

    • Concurrent gain on chromosome 9 and 18

• Clinical features

  • These tumors arise through out the  neuraxis in intimate association with ependymoma or its remnants

  • Rarely they may occur in cerebral cortex, subarachnoid space, in presacral and post sacral soft tissue

  • Ependymomas in 4th ventricle typically occur in children, where as supratentorial lesions are more common in older individuals

  • Supratentorial and intraparenchymal ependymomas are more likey to be anaplastic than those at other sites

  • Supratentorial ependymomas produce symptoms of increased intracranial pressure

  • Spinal ependymomas present in spinal cord proper or filum terminale are common in children. These tumors induce pain or patterns of motor and sensory deficits reflecting the affected segment 

•  Radiological findings

  • It presents as contrast enhancing mass with broad based origin in the floor of the 4th ventricle

  • Ependymomas can reach the cervical canal by way of the cisterna magna

  • Supratentorial ependymomas are frequently associated with a cyst and are often not intraventicular

  • Intraspinal ependymomas are sausage shaped, discrete, contrast enhancing masses that may be internally cystic.

• Gross findings

  • Supratentorial ependymomas enlarge centrifugally into surrounding brain or may intrude upon the ventricular system. Tumor appears fleshy, gray relatively circumscribed mass.

  • Intraparenchymal ependymomas are associated with cyst

  • Intraspinal ependymomas are gray and soft in consistency

• Microscopic findings

  • These tumors are usually well circumscribed and are 3 major types.

    • Cellular (with clear cell and papillary )

    • Tanycytic

    • Myxopapillary

  • Classic cellular 

    • It has both paucicellular and rich cellular areas

    • In the more cellular areas, nuclei are present in perivascular zones producing an anuclear region composed of tumor cell processes that converge upon vessel walls known as ‘perivascular pseudorosettes’

    • In paucicellular areas perivascular pseudorosettes are not present

    • Tumor cells have round to oval nuclei with granular salt and pepper chromatin

    • Small gemistocytes may be present

    • Glomeruloid microvascular proliferation may be present at the periphery of lesion

    • Vascular hyperplasia may also be present 

    • Spinal ependymomas of the cord may be cellular or tanycytic . 

      • Cellular ependymomas are similar to their intracranial counterpart, but perivascular pseudorosettes may be inconspicuous

      • Spinal intramedullary ependymomas may contain nodules of dense, collagenous tissue

      • Intramedullary ependymomas may induce diffuse piloid gliosis resembling pilocytic astrocytomas

    • Neoplastic ependymal epithelium may be present as true ependymal rosettes, canals or as discrete epithelial cells 

    • True rosettes and canals may be present with considerable fibrillarity in the background. True rosettes are present as clusters of cells with small lumen to large tubules or canals.

    • Normal ependyma overlies the ependymoma particularly if it is present in 4th ventricle

  • Papillary ependymoma 

    • these tumors are rare and have extensive surface epithelium

  • Clear cell ependymomas 

    •  Tumor cells have nuclear uniformity and perinuclear halos

    • Nuclei are rounder and larger than normal ependymoma

    • Depending upon the mitotic activity and the presence of microvascular proliferation, they are graded as Grade III

    • Unlike oligodendrogliomas nuclei in ependymoma are often clefted and show pseudoinclusions

  • Tanycytic ependymomas

    • They occur commonly in spinal cord but can also occur in brain

    • Ependymal cells are typically elongated and bipolar with long, fibrillated processes. hence it resemble Schwannoma or pilocytic astrocytoma

    • Perivascular rosettes are ill defined

    • Mitoses are rare

    • Tumors show dark pigment which is coarsely granular, lipochrome like and PAS positive

  • Heavy lipidized ependymoma with vacuolated cells can be seen

  • Few ependymomas shows cells cells with eosinophilic lysosome like cytoplasmic granules

  • Calcifications can occur and few may contain bone or cartilage

  • Myxopapillary ependymomas 

    • They are characterised by  delicate capsule, pseudopapillary architecture, perivascular and intercellular mucin deposition and tendency to cellular elongation

    • pseudopapillary architecture is due to adherence of tumor cells to blood vessels

    • Tumor cells are elongated or columnar with minor variation in nuclear size and shape

    • Due to elongated  cells with fibrillary process, it may be confused with Schwannoma

    • Mucin (PAS or Alcian blue positive ) is present in blood vessel walls, intracellular microcysts or as extravascular pools of mucin

    • some lesions contain foci of mucinous material and some may not have mucinous areas 

    • Typically in myxopapillary lesions solid, round structures with prickly appearance on reticulin stains are present which are referred as “Balloons”

  • Giant cell ependymoma

    •  this is commonly seen in filum terminal 

    • It is considered as degenerative phenomenon in otherwise typical myxopapillary lesion

    • cells have severe degree of nuclear pleomorphism resembling giant cell glioblastoma, but has few mitosis

    • Some intratcranial tumors also show severe nuclear pleomorphism  and are termed as “Gioant cell ependymoma”

• Grading 

  • Well differentiated ependymomas of brain and spinal cord – WHO grade II

  • Myxopapillary lesion – WHO grade I

  • Anaplastic ependymomas – WHO grade III

    • This is characterised by presence of vascular proliferation, high cellularity and more than focal brisk mitotic activity

    • Most of them are intracranial  

    • Cytologic atypia and necrosis in the absence of other feaures has no prognosic significance

• Immunohistochemistry 

  • Tumor cells are immunoreactive for 

    • GFAP 

    • S-100

    • Cytokeratin AE1/Ae3

  • Intracellular microlumen are posiive for EMA and CD99

• Differential diagnosis 

  • Schwannoma – They are strongly S-100 positive and GFAP negative. Ependymomas are also positive for S-100 but do not stain diffusely and strongly positive for GFAP

  • Meningiomas – They are GFAP negative and EMA positive

  • Pilocytic astrocytoma of the 4th ventricle – These tumors do not have perivascular pseudorosettes

  • Diffuse astrocyoma in posterior fossa – Due to paucicellular fibrillar areas in ependymomas but perivascular pseudorosettes will be absent in diffuse astrocytomas

  •  Neurocytomas 

    •  They also have prominen perivascular fibrillar areas resembling pseudorosettes. They are synaptophysin positive rather than GFAP

  • Oligodendroglioma 

    • These tumors have similarity with clear cell type of ependymomas however GFAP positive perivascular pseudorosettes, Nuclear grooves, clefts and pseudoinclusions suggests clear cell ependymoma

  • Choroid plexus papilloma

  • Metastatic adenocarcnoma – GFAP negative

• Treament and prognosis

  • Treatment is excision of the lesion

  • Intracranial ependymomas recur where as excision of spinal ependymomas have favourable prognosis

  • Less than 5% of cases disseminate via cerebrospinal fluid (mostly anaplastic  and myxopapillary types)

  • Distant metastasi occurs to the lungs and rarely to the presacral and post sacral soft tissue

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