Choroid Plexus Mass

Figure 1: Axial T2 MR image of the brain of a 24-year-old man shows a heterogeneous mass (arrows) in the temporal horn of the right lateral ventricle. Note a CSF cleft (arrowhead) anterolateral to the mass and low T2 signal intensity within the mass. There is no edema of the adjacent brain parenchyma.
Figure 2: Axial T1 post-contrast image shows homogeneous enhancement of the mass.

Facts: Choroid Plexus

• Starts differentiating in week 6 and has an adult appearance by week 20 of gestation
• Choroid plexus epithelium + capillaries are lined by ependymal cells. Capillaries are fenestrated allowing free movement of small molecules (lack of blood brain barrier), but epithelial cells connect each other with tight junction preventing passage of most macromolecules into CSF.
• Forms CSF and actively regulates CSF constituents

Choroid Plexus Mass

• Choroid plexus papillomas and carcinomas are common in young children (under 5 years old)
• Papillomas are benign tumor arising from choroidal epithelial cells; 5%-10% degenerate into carcinomas
• Papillomas are common in the first year of life, boys > girls, usually presenting with hydrocephalus (due to either CSF overproduction or obstruction in subarachnoid/intraventricular CSF pathways)

Imaging Findings: Choroid Plexus Papilloma

• Lobulated intraventricular mass; 25% calcified
• Isoattenuation on non-contrast CT
• Homogeneously enhanced after IV contrast administration
• On T2W MR image, central hypointensity is characteristic
• "Aggressive" papillomas may show irregular margins and grow into adjacent white matter causing edema

Suspect Choroid Plexus Carcinomas When:

• Presents with focal neurological deficits
• Grows into adjacent brain parenchyma, causing vasogenic edema
• Metastasize through CSF

Our case: choroid plexus papilloma in a young adult. Given our patient's age, differential diagnosis of meningioma, lymphoma and metastasis should also be entertained.

Reference:

Naeini RM, Yoo JH, Hunter JV. Spectrum of choroid plexus lesions in children. AJR 2009;192:32-40