Metastases to the choroid plexus from extracranial tumours are rare, but nonetheless should be included in the differential diagnosis of an intraventricular mass. They are most commonly found within the lateral ventricles, presumably because a large proportion of the choroid plexus is located there.
Choroid plexus metastases account for <5% of intracranial metastases in autopsy series, and <1% of clinically evident cerebral metastases 1,4. They are seen most commonly in adults, although have also been found in children with extracranial childhood tumours.
Tumour spread to the choroid plexus may occur through a haematogenous route via the anterior or posterior choroidal arteries 4,6, or through CSF seeding 4.
Tumours most likely to metastasise to the choroid plexus are renal cell carcinoma and lung cancer. Other tumours with documented spread to the choroid plexus include colon, gastric, breast, thyroid, and bladder cancers, melanoma and lymphoma.
Choroid plexus metastases may be seen on CT or MRI as either a solitary lesion, or as a component of disseminated intracranial metastatic disease. Reported complications which may be found on imaging include hydrocephalus and haemorrhage from an intraventricular metastasis 1.
Imaging appearance is variable. The lesion may be hypo or isodense on non-enhanced CT, and may demonstrate moderate or marked enhancement, more commonly homogeneous 6.
MRI is more sensitive than CT in the detection of small choroid plexus lesions.
With larger lesions, there may be peritumoural oedema or invasion into adjacent brain parenchyma.
Treatment and prognosis
These lesions may be amenable to surgical resection. Prognosis is variable and depends on the type and stage of the primary tumour, and extent of metastatic dissemination.
The differential diagnosis is that of other intraventricular masses that may arise in the relevant age group. In an adult patient, consider:
- intraventricular meningioma: particularly at the trigone of a lateral ventricle
- colloid cyst: when at the foramen of Monro 5
- central neurocytoma
- subependymoma: particularly if there is poor enhancement
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