Tumors of central and peripheral nervous system
CNS tumours
- Gliomas
- Tumours of brain parenchyma, from low grade to highly malignant (glioblastoma)
- Can be astrocytomas, oligodendrogliomas and ependymomas
- Astrocytomas can be diffuse or pilocytic. The diffuse form is the most common, and are usually found in cerebral hemispheres. Can cause seizures, headaches and focal neurologic defects. Morphologically, they are gray, infiltrative tumours, some are firm, others are soft (due to tissue necrosis)
- Oligodendrogliomas occur in middle aged patients, they have better prognosis than astrocytoma patients, they form gelatinous, gray masses which may have cysts, focal hemorrhage and calcification. The tumours also contain a network of capillaries
- Ependymomas often arise next to ependymal lined ventricular system in young people. Typically solid or papillary masses that extend from ventricular floor, tumour cells may be elongated and form perivascular pseudorosettes.
- Neuronal tumours
- Central neurocytoma is a low grade neoplasm found adjacent to ventricular system
- Gangliogliomas are tumours with a mix of glial elements (low-grade astrocytomas) and mature-appearing neurons
- Dysembryoplastic neuroepithelial tumour is a slow growing low grade childhood tumour
- Embryonal neoplasms
- Medulloblastoma - located in midline of cerebellum, gray, friable and well circumscribed. Highly cellular. Have a ‘small round cell’ appearance that is reminiscent of progenitor cells, hence embryonal neoplasm
- Meningiomas
- Tumours that arise from arachnoid meningothelial cells, often attached to the dura.
- Usually come to attention because of vague nonlocal symptoms or as an incidental finding.
- May be in association with CN8 (schwannomas) or glial tumours, may be part of neurofibromatosis type 2 disease
- There are atypical and anaplastic (malignant) meningiomas
- Familial tumour syndromes
- Tuberous sclerosis (AD)
- Von Hippel-Lindau disease (AD)
H&E, meningothelial meningioma: tumour cells wrapped into concentric whorls (centre). Whorls may calcify into laminated psammoma bodies.
Image: “Meningeotheliomatous meningeoma whorl formations” by Jensflorian, CC BY-SA 4.0, via Wikimedia Commons.
Remember: in adults most primary brain tumours are supratentorial (and metastases outnumber them); in children about 70% are infratentorial, in the posterior fossa - pilocytic astrocytoma, medulloblastoma and ependymoma of the fourth ventricle.
Peripheral nerve sheath tumours
- Schwannomas and neurofibromatosis type 2
- Schwannomas are benign encapsulated tumors that can occur in soft tissues, internal organs or spinal nerve roots
- Tumors that arise at nerve root or on the vestibular nerve can be associated with symptoms related to compression
- Most are sporadic, but 10% occur due to familial neurofibromatosis type 2, these patients are at risk of getting multiple schwannomas