University:
Western Sydney University
Course:
MEDI 2003 | Clinical Sciences 2
Academic year:

2024
Views:

359

Pages:

2
Author:

Mariam A.

Classification Systems of Brain Tumours WHO Grading System Histological grade is the main means of predicting the behaviour and guiding treatment, in contrast to the usual grading system, which appreciates the size/local tumour extent, presence/absence of regional nodal and distant metastases. Primary tumours rarely metastasise outside the CNS. The size of the tumour is less important than its location – e.g. a small meningioma may compress the brainstem and cause cardiorespiratory arrest, as opposed to a large lesion overlying the cerebral hemispheres with less drastic sequela. A grade of 1-4 is assigned to each of the tumour entities defined and classified by the WHO:  Grade 1 tumours – least aggressive  Grade 4 tumours – worst prognosis The traditional rigid definitions of benign vs. malignant tumours is difficult to apply to CNS tumours  Histologically bland tumours can infiltrate widely  Histological features suggestive of malignancy can be seen in low grade tumours (e.g. pilocytic astrocytoma)  Because of its location, even the most slow-growing tumours may not be resectable without compromising neurological function (and give rise to severe/fatal consequences) In general:  Grade 1 – low growth potential, possibly curable with surgery alone (e.g. pilocytic astrocytoma).  Grade 2 – also of low growth potential, but frequently recurs after surgery (since infiltrative and therefore incompletely removed); some also have potential to transform to grade 3 or 4 tumours (e.g. diffuse astrocytoma). Typical survival > 5 years.  Grade 3 – histological features of malignancy; patients receive radio and/or chemotherapy (anaplastic astrocytoma). Typical survival 2-3 years.  Grade 4 – necrotic lesions with even worse histological features, often rapidly progressive and fatal (glioblastoma). Typical survival < 12 months.  A number of factors need to be considered in planning treatment and prognosis: o Patient age o Co-morbidities that contraindicate chemoradiotherapy o Radiological localization and extent of tumour o Tumour volume removed by surgery o Genetic changes within the tumour (ex: oligodendrogioma and 1p/19q LOH - codeletion) WHO Classification of CNS Tumours The tumours are divided and subdivided into cell lineages emulated by the tumour (or from which the tumour originates). The following is a simplified classification system: 1. Tumours of neuroepithelial tissue - Glial tumours - Neuronal and neuro-glial tumours - Embryonal tumours (or ‘poorly differentiated’ tumours) - Others 2. Tumours that occur primarily within the CNS, but are not of the CNS cell lineage 3. Tumours of the meninges 4. Tumours of the cranial and paraspinal nerves 5. Metastatic tumours The most common primary brain tumors in adults are meningioma and glioblastoma.