Roughly 25-50% of all intracranial malignancies are estimated to be metastases in hospitalised patients. There is a great variation in imaging appearances, often presenting a diagnostic challenge.



Five primary tumors account for 80% of brain metastases:

1. lung cancer

2. renal cell carcinoma

3. breast cancer

4. melanoma

5. gastrointestinal tract adenocarcinomas (the majority colorectal carcinoma)


MRI features

T1: Typically shows iso- to hypointense signal. Hemorrhagic lesions may have an intrinsic high signal. Non-hemorrhagic melanoma metastases may have a high signal do to the paramagnetic properties of melanin. 


T1C+: The enhancement pattern can be uniform, punctate, or ring-enhancing, but it is usually intense. Delayed sequences may show additional lesions. 

T2: T2 imaging is usually hyperintense, though hemorrhage may alter this. 

FLAIR: FLAIR sequencing typically shows a hyperintense signal and hyperintense peri-tumoral oedema. 


DWI/ADC: The oedema is out of proportion with tumour size and appears dark on DWI. 

ADC demonstrates facilitated diffusion in oedema. 


Metastases T1
Metastasis of lung cancer T1
Metastases FLAIR
Metastasis FLAIR imaging
Metastases contrast
Metastasis of lung cancer T1 contrast enhanced