Adult Brain Tumours
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Direct answer
Adult brain tumours are mainly primary gliomas, meningiomas and metastases, and their presentation depends on location, growth rate and peritumoural oedema more than on histology alone. Glioblastoma, the most aggressive primary tumour, produces a rapidly evolving focal deficit or raised intracranial pressure and shows an irregular ring-enhancing mass with central necrosis on MRI. Meningioma is an extra-axial, dura-based tumour with a dural tail, while multiple metastases sit at the grey-white junction and usually arise from lung, breast, melanoma, kidney or colon primaries.
What you must remember
- Glioblastoma: IDH-wildtype grade 4 astrocytoma with necrosis and microvascular proliferation; standard care is maximal safe resection, radiotherapy and concurrent temozolomide, with a prognosis measured in months to a few years.
- IDH status: IDH-mutant gliomas behave better than IDH-wildtype glioblastoma, and the molecular result now shapes classification as much as histology.
- Meningioma: extra-axial, dural-based and often calcified, more common in women and frequently WHO grade 1; asymptomatic small lesions may be observed, while symptomatic ones are resected.
- Metastases: the commonest brain tumours in adults, usually multiple lesions at the grey-white junction with disproportionate oedema; melanoma, renal and choriocarcinoma deposits are prone to haemorrhage.
- Primary CNS lymphoma: periventricular, ring-enhancing lesions in immunocompromised patients; corticosteroids before biopsy can destroy the diagnostic yield.
- Oedema control: dexamethasone relieves peritumoural oedema, and levetiracetam is the usual antiseizure drug choice in tumour-related seizures.
A worked case: a ring and a dural tail
A 58-year-old man has two months of morning headaches, vomiting and left arm weakness, and MRI shows an irregular ring-enhancing right frontal lesion with wide oedema. Glioblastoma is the leading possibility, but a solitary metastasis must be excluded with chest imaging.
- Exclude the mimics: Chest imaging excludes a solitary metastasis, and diffusion restriction separates an abscess.
- Control oedema: Dexamethasone is started for the peritumoural oedema.
- Plan tissue: Neurosurgical resection is planned to obtain tissue for diagnosis.
- Test the molecular markers: Histology with IDH and MGMT testing guides subsequent chemoradiation.
A 45-year-old woman with headaches and a convexity lesion shows a dural tail and calcification on CT. That picture is a meningioma, and the decision is observation or resection depending on symptoms.
A third patient with a known lung primary and several ring-enhancing lesions at the grey-white junction is a metastatic picture, so systemic staging and a tissue diagnosis from the most accessible site precede any heroic surgery. Performance status and the wishes of the patient shape how aggressive treatment should be, and this is discussed before any operation.
Where the examiner sets the trap
Examiners set the same few traps in brain tumour questions.
- Trap: Treating a solitary ring-enhancing lesion in HIV as lymphoma without considering toxoplasmosis. Correct: Toxoplasmosis responds to empirical treatment and should be considered before tissue, whereas lymphoma does not. Steroids given for a presumed toxoplasma lesion can make a lymphoma biopsy non-diagnostic.
- Trap: Calling meningioma benign without qualification. Correct: Some are atypical or anaplastic and need radiotherapy after resection.
- Trap: Searching for a primary only in the brain when several lesions appear with no known source. Correct: The skin, lungs and breasts should be examined, because melanoma and lung cancer are the usual suspects.
The viva answer that impresses names the imaging clue, the steroid trap and the next investigation in one breath.
Frequently asked questions
What is the typical MRI appearance of glioblastoma?
Glioblastoma appears as an irregular ring-enhancing mass with central necrosis and surrounding T2 and FLAIR oedema. It often crosses the corpus callosum to produce a butterfly pattern, which favours a high-grade glioma over a single metastasis.
How does meningioma differ from metastasis on MRI?
Meningioma is extra-axial and dura-based, with a dural tail and often calcification, whereas metastases are intra-axial, usually multiple, and sit at the grey-white junction with disproportionate oedema. Biopsy or resection confirms the diagnosis when the appearance is atypical.
Which primary tumours most often metastasise to the brain?
Lung, breast, melanoma, renal cell carcinoma and colorectal cancer are the common sources of brain metastases. Melanoma and renal primaries are prone to haemorrhage, which can make the lesions look different on imaging.
Why should steroids be avoided before biopsy when lymphoma is suspected?
Corticosteroids can rapidly shrink primary CNS lymphoma and reduce the yield of histological diagnosis. When the patient is stable, biopsy comes first, and steroids are reserved for clinically necessary oedema control.