Choroid plexus papillomas are an uncommon, benign (WHO grade I) neuroepithelial intraventricular tumour which can occur in both the paediatric (more common) and adult population.
On imaging, these tumours are usually identified in the fourth ventricle in adults and in the lateral ventricles in the paediatric population. They commonly present as a solid vascular tumour with vivid frond-like pattern enhancement. In a quarter of cases, speckled calcifications are present.
Overall these tumours account for approximately 1% of all brain tumours, 2-6% of all paediatric brain tumours and 0.5% of the adult brain tumours. They are, however, disproportionately represented in brain tumours in children under the age of 1 10. Approximately 85% of all choroid plexus papillomas occur in children under the age of 5 years 4.
Interestingly, the age distribution is very different for infratentorial (fourth ventricle) versus supratentorial (usually lateral ventricle). The vast majority of supratentorial tumours are seen in children, whereas posterior fossa tumours are evenly distributed at all age groups, including the elderly 9.
Hydrocephalus is very common, seen in over 80% of cases 4. Although the exact mechanism remains uncertain, it is believed to be due to a combination of CSF overproduction and decreased arachnoid granulation resorption.
Choroid plexus papillomas are WHO grade I lesions, with a low mitotic rate (<2 mitoses are present per 10 high-power field), and to a lesser degree histological features, distinguishing them from atypical choroid plexus papillomas (WHO grade II) and choroid plexus carcinomas (WHO Grade III) 7,10.
and typically appear as cauliflower-like masses 4,10.
These tumours demonstrate papillary structures with a delicate fibrovascular core lined by columnar or cuboidal epithelial cells with vesicular basal nuclei. Their appearance is very similar to normal choroid plexus 7.
- cytokeratins: positive (especially CK7)
- vimentin: positive
- usually positive
- also found in normal choroid plexus
- better prognosis if positive 10
- better prognosis if positive 10
- usually positive and specific
- potassium channel also found in normal choroid plexus 10
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 compared to adjacent brain; may be somewhat hypointense
- iso to hyperintense
- small flow-voids may be seen within the tumour
- T1 C+ (Gd): marked enhancement, tends to be homogeneous
- decreased NAA
- increased Cho
Being very vascular tumours, these masses demonstrate intense vascular blush on angiography. Enlarged choroidal arteries may be seen feeding the tumour, with shunting 4.
Treatment and prognosis
Total excision should be the aim of therapy and is curative in a vast majority of cases. Overall there is 90% 1-year-survival, and 77% 5-year-survival 10.
The differential is essentially that of other choroid plexus tumours:
- 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 7
- 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:
In adults, and depending on location, consider:
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- 7. Smith A, Smirniotopoulos J, Horkanyne-Szakaly I. From the Radiologic Pathology Archives: Intraventricular Neoplasms: Radiologic-Pathologic Correlation. Radiographics. 2013;33 (1): 21-43. Radiographics (full text) - doi:10.1148/rg.331125192
- 8. Jinhu Y, Jianping D, Jun M et-al. Metastasis of a histologically benign choroid plexus papilloma: case report and review of the literature. J. Neurooncol. 2007;83 (1): 47-52. doi:10.1007/s11060-006-9300-4 - Pubmed citation
- 9. J E A Wolff, M Sajedi, R Brant, M J Coppes, R M Egeler. Choroid plexus tumours. British Journal of Cancer. 87 (10): 1086. doi:doi:10.1038/sj.bjc.6600609
- 10. Louis DN, Ohgaki H, Wiestler OD, Cavenee WK "WHO Classification of Tumours of the Central Nervous System. 4th Edition Revised" ISBN: 9789283244929