Choroid plexus papillomas (CPP) are benign brain tumors.
These highly vascular tumors retain the physiological function of choroid plexus and thus lead to overproduction of cerebrospinal fluid (CSF), besides obstructing the CSF pathway.
The overall incidence is less than 1% of all intracranial tumors.
They occur in the lateral ventricle in most cases, but have also been described in the third or fourth ventricles 1)
Most of these tumors occur in the lateral ventricles in neonates.
Third ventricle location is uncommon, limited to a few case reports.
In two cases of choroid plexus papilloma reported at 21 weeks of pregnancy, the diagnosis was suspected because of ventriculomegaly. Both pregnancies were terminated and pathological examination showed bilateral papillomas of the choroid plexus 6).
They are histologically classified as plexus papilloma, atypical plexus papilloma, and plexus carcinoma.
They can correspond to two different etiologies: papilloma, which is a benign tumor, and carcinoma of the choroid plexus.
Imaging is fairly sensitive and specific in affording the diagnosis of this tumor.
On imaging choroid plexus papillomas are characterised by vividly enhancing, usually intraventricular, masses. Hydrocephalus is common.
Unlike most other brain tumours, which are more common in the posterior fossa in children and supratentorial compartment in adults, the relationship is reversed for choroid plexus papillomas:
adults: most often (70%) occur in the fourth ventricle children: most often occur in the lateral ventricles, with a predilection for the trigone Third ventricular, cerebellopontine angle, parenchymal and even pineal region tumours have also been described.
The tumours are usually well-defined lobulated masses, either iso- or somewhat hyperdense compared to the adjacent brain. There is associated hydrocephalus. They usually homogeneously enhance, demonstrating with an irregular frond-like pattern, resulting in a cauliflower-like appearance. If there is markedly heterogeneous contrast enhancement, a choroid plexus carcinoma should be suspected 4.
Fine, speckled calcification is seen within the tumour in approximately 25% of cases 4.
The frond-like morphology of the tumour can usually be seen, especially following contrast administration. Varying degrees of associated hydrocephalus are also present in almost all cases.
T1: typically isointense cf. to adjacent brain; may be somewhat hypointense.
T2 iso to hyperintense
small flow-voids may be seen within the tumour
T1 C+ (Gd): marked enhancement, tends to be homogeneous
increased Cho 7).
The differential is essentially that of other choroid plexus tumors:
atypical choroid plexus papilloma: indistinguishable, but far less common
choroid plexus carcinoma: can be very difficult on imaging alone almost exclusively found in young children heterogeneous contrast enhancement may show parenchymal invasion
choroid plexus metastases When located in the posterior fossa in children (less common) other tumours to be considered include:
medulloblastoma atypical teratoid/rhabdoid tumour (AT/RT)
ependymoma In adults, and depending on location, consider:
ependymoma intraventricular meningioma subependymoma central neurocytoma exophytic glioma
Total removal is possible for 96% of papillomas and for 61% of carcinomas. Surgical procedures are associated with significant operative morbidity and mortality due to uncontrolled bleeding. The prognosis is widely variable between the two forms, with a survival rate at 5 years of approximately 100% for papillomas and 40% for carcinomas 8).