Differential diagnosis
multifocal glioblastoma multiforme
- Well defined
- On perfusion maps, the increased relative cerebral blood volume (rCBV) has sharp margin
- On MR spectroscopy, absent NAA and presence of a lipid peak
Hence, this is cerebral metastasis
As metastasis is from an extra cerebral site, neurons are not present in it. NAA which is a neuronal marker is thus absent.
Multifocal GBM has infiltrating margins, the elevated rCBV decreases in a graded manner towards the normal brain parenchyma and MR spectroscopy shows decrease in but not complete absence of NAA as few neurons would be present.
Mechanism of brain metastases – majority disseminate by hematogenous spread.
The anatomic distribution generally parallels regional cerebral blood flow, with a predilection for the grey-white matter junction and for the border zone between middle and posterior cerebral artery territories
Common primary tumours that metastasize to the brain
- Lung cancer ( Adenocarcinoma and small cell lung cancer )
- Breast cancer ( Ductal carcinoma ); this has a propensity to metastasize to the cerebellum and the posterior pituitary gland
- Gastrointestinal malignancies
- Melanoma
- Germ cell tumour
- Thyroid cell cancer
By contrast, prostate cancer, ovarian cancer and Hodgkin’s disease rarely metastasize to the brain.