Description
Choroid plexus carcinoma (CPC) is a rare, aggressive malignant neoplasm that originates from the epithelial cells of the choroid plexus. It’s a grade III tumour in the World Health Organisation (WHO) classification, primarily seen in paediatric patients, with a propensity to cause overproduction of cerebrospinal fluid (CSF), often leading to hydrocephalus.
Pathogenesis
While the exact pathogenesis of CPC remains unclear, it’s considered a genetic disorder with an association with the TP53 tumour suppressor gene mutation and Li-Fraumeni syndrome.
Subtype
No recognised subtypes of CPC exist.
Epidemiology, Risk Factors & Associations
- Constitutes 2-4% of all paediatric brain tumours.
- Frequently diagnosed in children under 2 years of age.
- Association with Li-Fraumeni syndrome (a TP53-related disorder, estimated 3%) and familial adenomatous polyposis (FAP) (mutations in the APC).
Clinical Features
Symptoms primarily relate to the overproduction of CSF and resultant hydrocephalus, including headache, nausea, vomiting, and lethargy. Neurological deficits may occur based on tumour location. Infants may present with macrocephaly and developmental delay.
Complications
Complications include hydrocephalus, CSF overproduction, metastasis, and recurrence after treatment.
Pathological Features
Histopathology
- Macroscopic: Masses tend to be large, poorly circumscribed, with possible haemorrhage and necrosis.
- Microscopic: Characterised by increased cellularity, nuclear pleomorphism, high mitotic activity, and necrosis.
Radiological Features
General Features
- Characteristically presents as a large, lobulated, intraventricular mass.
- Calcifications are uncommon.
CT
- Non-contrast: Hyperdense to surrounding brain parenchyma.
- Contrast-enhanced: Intense and heterogeneous enhancement due to its vascularity and necrotic areas.
MRI
- T1WI: Isointense to slightly hypointense to brain parenchyma.
- T2WI: Hyperintense signal due to high water content.
- T1 C+: Heterogeneous enhancement due to necrotic areas within the tumour.
- DWI/ADC: Restricted diffusion due to high cellularity of the tumour.
Grading and Staging
CPCs are WHO grade III tumours. There is no specific staging system for these tumours.
Diagnosis
The diagnosis is usually suspected based on imaging and clinical presentation, and confirmed by histopathological analysis post-surgical resection.
Differential Diagnosis
- Choroid Plexus Papilloma (CPP): Less aggressive and less cellular compared to CPC, with a more regular pattern of enhancement and typically lacks signs of necrosis. CPPs are often well-circumscribed with no signs of adjacent brain invasion, whereas CPCs are usually poorly circumscribed and invade surrounding brain structures. Calcifications are more common in CPP compared to CPC.
- Medulloblastoma: Although it typically arises in the cerebellum and manifests in older children, it could be considered in the differential diagnosis due to its similar imaging characteristics. Medulloblastomas are hyperdense on CT and demonstrate intense contrast enhancement. However, these tumours typically induce cerebellar signs and symptoms, which help distinguish them from CPCs. Furthermore, medulloblastomas often cause obstructive hydrocephalus secondary to fourth ventricle obstruction, whereas CPCs directly produce excessive CSF leading to communicating hydrocephalus.
- Ependymoma: Another intraventricular tumour; however, it often presents with a different age distribution and possesses calcifications. Ependymomas are usually found in older patients and are more commonly located in the posterior fossa. On imaging, they demonstrate a characteristic “popcorn” appearance with a mix of cysts, calcifications, and haemorrhages.
- Atypical teratoid rhabdoid tumour (ATRT): ATRT can be differentiated from CPC by its unique characteristic of a diverse tissue component which results in a heterogeneous appearance on imaging studies. ATRT is also associated with a higher frequency of haemorrhage and necrosis compared to CPC.
- Metastatic disease: Metastases can be differentiated based on a patient’s age and clinical history. In adults, multiple intraventricular lesions would be more suspicious for metastatic disease, while in children, CPC would be higher on the differential. Metastatic lesions would also lack the intense and uniform contrast enhancement typical of CPC.
Management
The mainstay of treatment includes maximal safe surgical resection, followed by adjuvant chemotherapy and/or radiotherapy. Genetic counselling is essential in patients with identified germline mutations. Neurosurgical and oncological input is necessary for optimal care.