Choroid plexus papillomas are WHO grade 1 tumours generally presenting by 5 years of age, which arise in the lateral ventricular atrium and demonstrate a lobulated frond-like margin and homogenous hyperenhancement.
Description
Choroid plexus papillomas (CPPs) are rare, benign WHO Grade I neoplasms originating from the epithelial cells of the choroid plexus, typically presenting within the first decade of life. These tumours are primarily known for their overproduction of cerebrospinal fluid (CSF), often leading to paediatric hydrocephalus.
Pathogenesis
The precise pathogenesis of CPP remains unclear. It is hypothesised to arise from choroidal epithelial cells, which results in excessive CSF production and can lead to obstructive hydrocephalus.
Subtype
There are no recognised subtypes of CPP.
Epidemiology, Risk Factors & Associations
- Accounts for approximately 1-4% of all paediatric brain tumours
- Predominantly found in children, especially during the first year of life, but can also occur in adults
- Rarely present in newborn period or diagnosed on prenatal ultrasound
- Patients with Li-Fraumeni Syndrome and Aicardi syndromes are at increased risk.
Clinical Features
Presentation is typically dependent on the age of the patient and the location of the tumour. Common symptoms may include:
- Signs and symptoms of raised intracranial pressure due to hydrocephalus, such as headache, nausea, vomiting, and lethargy. Papilloeodema and bulging fontanelles may be present.
- Infants may present with macrocephaly and developmental delay.
Complications
Potential complications include
- Hydrocephalus, likely multifactorial; CSF overproduction, obstruction of CSF pathways by mass effect, and obstruction of arachnoid granulations secondary to proteinaceous or haemorrhagic CSF.
- Rarely, malignant transformation into choroid plexus carcinoma.
Pathological Features
Histopathology
- Macroscopic: These tumours are lobulated, well-circumscribed masses with frond-like margins and a shiny greyish-pink surface.
- Microscopic: CPPs resemble normal choroid plexus and display a papillary architecture lined by a single layer of cuboidal to columnar cells.
Radiological Features
General Features
- Characteristically demonstrates an intraventricular mass lesion at the lateral ventricular atrium with frond-like margins giving a popcorn or cauliflower appearance.
- Most commonly arises in the atrium of the lateral ventricle (70% of cases), more commonly on the left.
- In adults, CPP more commonly arise in the 4th ventricle.
- Communicating hydrocephalus due to overproduction of CSF or non-communicating due to obstruction of the foramen of Monro.
- Calcifications may be seen.
- Tumour may expand the ventricle and bow the septum pellicudum.
- Irregular heterogenous mass invading the brain and inciting extensive vasogenic oedema may suggest choroid plexus carcinoma, although ependymal and brain invasion can also be seen in aggressive papillomas.
CT
- Non-contrast: Hyperdense (or isodense) relative to brain parenchyma, possibly due to high protein content of the tumour. Hydrocephalus. Punctate calcific foci may be seen.
- Contrast-enhanced: Show intense and nearly homogeneous enhancement due to the vascularity of the tumour. Enlargement of the anterior or posterior choroidal artery may be seen.
MRI
- T1WI: Isointense to slightly hypointense compared to brain parenchyma.
- T2WI: Hyperintense signal, reflecting the high water content. Flow voids may be demonstrated.
- T1 C+: Shows strong homogeneous enhancement and lobulated, frond-like margin of the tumour
- GRE/SWI: Internal susceptibility effect may represent haemorrhage or calcifications
- DWI/ADC: No diffusion restriction, differentiating it from other high cellular tumours.
Grading and Staging
CPPs are categorised as WHO Grade I tumours, indicative of their typically benign nature. There is no specific staging system applicable to these tumours.
Diagnosis
The diagnosis is typically suspected based on clinical presentation and imaging features, primarily on MRI. Definitive diagnosis is confirmed by histopathological examination following surgical resection.
Differential Diagnosis
- Choroid plexus carcinoma: Imaging cannot reliably differentiate between papilloma and carcinoma, though heterogenous enhancement favours carcinoma. Both lesions may show parenchymal invasion and subarachnoid spread of tumour. Choroid plexus carcinomas have high mitotic activity, areas of necrosis, and hypercellularity (v.s. papillary architecture and simple columnar epithelium)
- Ependymoma: Heterogeneous signal intensity with calcification and haemorrhages, typically in different ventricular locations.
- Medulloblastoma: Predominantly found in the cerebellum of children and showing different signal characteristics.
- Central neurocytoma: Typically arises from the septum pellucidum as a bubbly mass, extending into the lateral ventricles. Most common in ages 20-40.
- Sturge-Weber syndrome: Enlargement and hyperenhancement of choroid plexus. Associated findings of cerebral hemiatrophy with tram-track calcification, enhancing pial angiomatosis and choroid angioma with buphtalmos.
Prognosis
The prognosis is excellent with complete surgical resection of papillomas. By comparison, choroid plexus carcinomas only have a 40% 5-year survival rate.
Management
The mainstay of treatment is surgical resection to remove the tumour and relieve symptoms of increased intracranial pressure. In some cases, ventricular shunting may be necessary to manage hydrocephalus. Neurosurgical consultation is warranted for definitive management.