Choroid plexus papilloma

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Definition

Choroid plexus papilloma is a papillary, intraventricular tumor derived from choroid plexus epithelium. Choroid plexus papilloma corresponds to WHO Grade I glioma.

Epidemiology

Choroid plexus papilloma accounts for less than 1% of all brain tumors, and about 2-4% of those that occur in children. 10-20% of all choroid plexus papillomas aise in the first year of life. The average incidence is 0.3 per 1,000,000. About 80% of choroid plexus papillomas arise in patients under the age of 20. Its linked to Li-Fraumeni syndrome and von Hipel-Lindau syndrome.

Localization

These tumors arise most frequently in the lateral (50%), 4th (40%) and 3rd (5%) ventricles. Usually occur in the lateral ventricle of children (more commonly the left side) and in the fourth ventricle in adults (in adults the tumor is more common in men).

Imaging

On MRI, choroid plexus papillomas appear as well circumscribed, cauliflower-like lesions arising from the ventricular surface. Cystic changes and intra-tumoral hemorrhage are not uncommon. Ventricular englargement due to overproduction of CSF, obstruction of CSF pathways by the tumor mass, subarachnoid scarring due to recurrent bleeding from the tumor.


Left: Contrast-enhanced T1-weighted MR images showing a choroid plexus papilloma that developed in the third ventricle. The vascular tumor pedicle arising from the choroid plexus and the associated hydrocephalus are typically observed in cases of these lesions. Right: An MR image showing a choroid plexus carcinoma of the lateral ventricle without hydrocephalus. In children such appearances can be similar to those of an ependymoma or an intraventricular meningioma.
Angiograms obtained in a 3-year-old boy with a choroid plexus carcinoma of the lateral ventricle. Left: Anteroposterior view of the left vertebral injection showing a hypervascularized lesion fed by a choroidal branch from the right posterior cerebral artery. Center: Selective injection of the right posterolateral choroidal artery. Right: Anteroposterior view of the vertebral artery injection after embolization.


Histopathology

Choroid plexus papilloma is a benign, papillary tumor composed of fronds of delicate fibrovascular connective tissue covered by a single layer of uniform cuboidal to columnar epithelial cells with round or oval, monomorphic nuclei located adjacent to the basal surface. Mitoses, brain invasion and necrosis are absent. Papilloma is distinguished from normal choroid plexus by cellular pleomorphism, nuclear hyperchromasia, and moderate mitotic activity; often calcifies. CSF protein levels usually elevated, >50% have xanthrochromia. Immunohistochemically, the tumors may display cytokeratins and vimentin. They are GFAP positive in 25-55% of samples.


Molecular genetics

While choroid plexus papilloma may occur in the setting of Li Fraumeni syndrome, TP53 mutations have not been reported in cases of sporadic choroid plexus papilloma. Hyperdiploidy of chromosomes 7, 9, 12, 15, 17, and 18 are common. In particular, duplication of chromosome 9p has been thought to give rise to abnormal growth of the choroids plexus.

Atypical Choroid Plexus Papilloma

Definition: The diagnostic category of atypical choroid plexus papilloma has been established to identify the frequent difficulty in distinguishing between choroid plexus papilloma and carcinoma. These tumors show only one or a few histopathologic features of maliganancy, e.g. increased cellularity or increased mitotic activity. Atypical choroid plexus papilloma corresponds to WHO Grade II glioma.

Treatment

Surgical resection is the preferred treatment with gross total resection the goal. The 10 year survival with GTR is 85% versus 56% with a subtotal resection. Secondary goals of surgery include relieving hydrocephalus.

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