Page 637 - Concise Pathology for Exam Preparation ( PDFDrive )

622 SECTION II Diseases of Organ Systems

Molecular genetics: Possible association of spinal ependymomas with NF2 gene is

being examined.
Gross pathology:
• Well-circumscribed, typically solid papillary, friable; may show cystic areas
• Arise from the roof or floor of 4th ventricle; fill the ventricular cavity and may
invade the cerebellum and medulla

• Calcification is seen in 15% of the cases.
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Microscopy:
• ‘Epithelial-like cells’ with regular round to oval nuclei and granular chromatin,
dispersed in a fibrillary background (GFAP-positive)
• Gland-like/round/elongated structures called rosettes/canals
• Perivascular pseudorosettes (tumour cells arranged around vessels with thin epen-
dymal processes directed towards the wall of the blood vessel)
• Prognosis poor despite slow growth and lack of anaplasia (attributed to frequent
dissemination in CSF and poor surgical accessibility)
Variants:
• Anaplastic ependymoma: Shows increased cell density, high mitotic rate, areas of
necrosis, dedifferentiation (Grades III/IV histology)
• Myxopapillary ependymoma: Arises from filum terminale:
• Composed of papillae with a core of dilated blood vessels covered by 1–2 layers
of cuboidal cells. The fibrovascular stroma may show mucoid degeneration.
• Prognosis depends on completeness of surgical resection.
• Subependymoma:
• Diffuse proliferation of subependymal fibrillary astrocytes and ependymal cells
• Small, multiple and symptomless
• Usually arise in the 4th ventricle
• Solid, sometimes calcified; if large, may lead to hydrocephalus
Choroid plexus papilloma
4.
(a) In adults, usually arise from the 4th ventricle and cerebellopontine angle. In chil-
dren, lateral ventricles are a common location.

(b) May cause generalized enlargement of ventricular system and subarachnoid space.
Ventricular obstruction may lead to hydrocephalus.
Gross: Cauliflower-like, soft, friable and crumbling pink mass
Microscopy: Specialized ependymal cells recapitulate structure of normal choroid
plexus.
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Prognosis: Difficult to remove and commonly recurrent

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Neuronal Tumours

These are tumours containing mature-appearing neurons (ganglion cells). Gangliocytomas

contain only neurons and gangliogliomas contain neurons admixed with glial cells.

Poorly Differentiated or Embryonal Neoplasms
Thought to be neuroectodermal in origin; however, rarely express, if any, phenotypic
markers of mature cells of nervous system, eg, medulloblastoma and atypical teratoid/
rhabdoid neoplasm.
Medulloblastoma
• Constitutes 20–25% of all intracranial tumours in children.

• Exclusively located in cerebellum (three-fourth involve midline or vermis; rest in cerebellar

hemispheres). Also occurs along the cerebellopontine angle.

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• Molecular genetics: Loss material from short arm chromosome 17 usually in
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the setting of an abnormal chromosome derived from duplication of the long arm

of chromosome 17. The identity of the tumour suppressor gene lost not clear

(Not P53).

Gross pathology: Fourth ventricle compressed or invaded by an unencapsulated, grey white,

soft, haemorrhagic and friable mass without cystic change, leading to hydrocephalus.

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