Incidence: 0.5–0.6% of all primary intracranial tumors; 2–5% of pediatric brain tumors; 5% of all supratentorial tumors in children; 60–70% of all choroidal tumors

Age: up to 20% <1 year of age; in 75% <2 years of age; in 86% <5 years of age; M >>F

Path: large aggregation of choroidal fronds producing great quantities of CSF; occasionally found incidentally on postmortem examination

Pathophysiology: abnormal rate of CSF production of 1.0 mL/min (normal rate = 0.2 mL/min)

Subdivision:

1. Choroid plexus papilloma (CPP) (WHO grade I)
2. Atypical choroid plexus papilloma (WHO grade II) ≥2 mitoses per 10 randomly selected high-power fields
3. Choroid plexus carcinoma (CPC) (WHO grade III) >5 mitoses per high-power field

CPP÷CPC = 5÷1

Imaging does not allow distinction between subdivisions.

All subtypes may demonstrate CSF dissemination → imaging of the entire neuroaxis is recommended!

May be associated with: von Hippel-Lindau syndrome (papillomas in unusual locations), Aicardi syndrome, Li-Fraumeni syndrome

• signs of increased intracranial pressure

Location: anywhere within choroid plexus epithelium

1. glomus of choroid plexus in atrium (trigone) of lateral ventricles (in 50% of adults, in 80% of children), L >R (in children); M=F
2. 4^th ventricle (40%) + cerebellopontine angle (in adults); M÷F = 3÷2
3. 3^rd ventricle (10%)
4. multiple in 5–7%

• large mass with papillary / smooth lobulated border (DDx from other intraventricular neoplasms)
• small foci of calcifications (common)
• ± cystic areas within tumor
• engulfment of glomus of choroid plexus (DISTINCTIVE feature)
• asymmetric diffuse ventricular dilatation = communicating hydrocephalus
  Cause:
  1. CSF overproduction by neoplasm
  2. obstruction of CSF absorption ← proteinaceous exudate / repeated occult hemorrhage
  3. direct obstruction of CSF pathway)
• dilatation of temporal horn in atrial location (obstruction)
• occasionally growth into surrounding white matter (more commonly a feature of choroid plexus carcinoma)
• septa / cysts within ventricular system ← inflammatory reaction to tumor / tumoral hemorrhage

CT:

• iso- / mildly hyperattenuating homogeneous mass
• ± calcifications and foci of hemorrhage

CECT:

• intense homogeneous enhancement ← very vascular lesion

MR:

• iso- to slightly hypointense lesion on T1WI + iso- to hyperintense on T2WI relative to white matter
• flow voids (common)
• surrounded by hypointense signal on T1WI + hyperintense signal on T2WI (CSF)
• intraventricular enhancing island of tumor on Gd-DTPA + retention of contrast within tumor interstitium

MR spectroscopy:

• marked choline peak WITHOUT N-acetylaspartate / creatine peak; elevated lactate level for carcinomas

US:

• echogenic mass adjacent to normal choroid plexus

Angio:

• enlarged choroidal artery if neoplasm located in atrium ← supplied by anterior + posterior choroidal arteries

Cx:

1. Transformation into malignant choroid plexus papilloma = choroid plexus carcinoma (in 5%)
2. Hydrocephalus (in children) ← increased intracranial pressure from CSF-overproduction
3. Tumor infarction ← twist of pedicle

Rx: surgical removal (24% operative mortality) cures hydrocephalus

Prognosis: 97% 5-year survival rate for papilloma; 26–43% 5-year survival rate for carcinoma

DDx: intraventricular meningioma, ependymoma, metastasis, cavernous angioma, xanthogranuloma, astrocytoma