Choroid plexus carcinoma

Choroid plexus carcinoma (CPC) is a malignant neoplasm arising from the choroid plexus.  It is classified as a WHO grade III tumour and while there is considerable overlap in imaging characteristics it carries significantly poorer prognosis than choroid plexus papilloma (CPP).

Epidemiology

Choroid plexus carcinomas occurs predominantly in children, typically in the first 5 years of life. They are rare, far less common than choroid plexus papillomas (which account for 80% of primary choroid plexus tumours), representing only 1-4% of paediatric brain tumours ^5,7. 

Clinical presentation

As is the case with choroid plexus papillomas, presentation usually is as a result of hydrocephalus. Symptoms thus include increasing head circumference and headaches. Papilloedema may be visible on fundoscopy. In addition, choroid plexus carcinomas have a tendency to invade adjacent brain and thus may present with focal neurological dysfunction ⁷. 

There is an association with Li-Fraumeni syndrome ⁵. 

Pathology

They originate from choroid plexus epithelium and typically arise de novo; some may via malignant transformation of a choroid plexus papilloma ⁴. 

Macroscopically, they are lobulated masses with cystic and necrotic areas with loss of the papillary cytoachitecture seen in both the normal choroid plexus and CPP ⁴.  Microcalcifications and haemorrhage may be present. Brain parenchymal invasion is a feature, and if present distinguishes choroid plexus carcinomas from choroid plexus papillomas.

The most common underlying genetic mechanism identified in their formation is dysfunction of the p53 tumour suppressor gene. There has also been association with Simian Virus 40 (SV40) on the basis of this virus' DNA having been identified in up to 50% of cases ⁵. 

Radiographic features

Choroid plexus carcinomas are markedly enhancing intraventricular tumours, usually arising in the trigone of a lateral ventricle.

Hydrocephalus may be present but is less likely than with choroid plexus papillomas. In CPC, hydrocephalus is generally a consequence of CSF pathway obstruction by the mass or a metastases whereas in CPP, there is at least a component of CSF overproduction. 

CT

On non-contrast CT choroid plexus carcinomas are heterogeneous and typically iso to hyperdense to grey matter.  Calcification may be seen in 20 - 25-25% of cases.

Contrast enhanced  is usually prominent but heterogeneous with areas of necrosis and cyst formation evident. 

 MRI

Reported signal characteristics include

• T1 -: iso- to hypointense
• T2 -: iso- to hypointense with hyperintense necrotic areas
• T2* GRE -: blooming from calcifications / haemorrhage/haemorrhage
• T1 C+ (Gd) -: can show marked, heterogeneous enhancement.  

The tumours may have CSF seeding -, therefore imaging of the entire neural axis is recommended prior to surgery.

Treatment and prognosis

Choroid plexus carcinomas are rapidly growing tumours with a 40% 5-year survival. Brain invasion and CSF seeding are poor prognostic factors ³.

Surgical en-bloc resection is the mainstay of treatment and can result in cure, achieved in as many as 50% of cases, but this result has only been reported in some selected series ⁵. In general survival seems to be much worse than this, and hinges upon the ability to achieve gross complete macroscopic resection. In such cases a 5-year survival of up to 86% can be achieved. In cases where resection is incomplete, 5-year survival is much lower 26% ⁶. Both radiotherapy and chemotherapy are used ⁵. 

Differential diagnosis

General imaging differential considerations include:

• choroid plexus papilloma
  • homogeneous
  • lack of necrosis,
  • lack of cerebral parenchymal invasion
  • it is difficult to categorically distinguish CPP from CPC and as such  biopsy is required.
• central neurocytoma
  • older demographic
  • usually in the body of the lateral ventricle, typically abutting the septum pellucidum
• intraventricular meningioma
  • older demographic 
  • more homogeneous outline and contrast enhancement
• choroid plexus metastasis
  • rare in children

Further differentials to be considered in a large tumour, where the intraventricular origin may be difficult to ascertain, include PNET and GBM.

See also

• intraventricular masses (differential)
• intraventricular masses - an approach