They are rare intraventricular tumors that arise from choroid epithelium and account for less than 1%% of all intracranial  tumors.

They are more common in children than in adults, with a mean patient age of 5.2 years.

20% of them occur in patients younger than 1 year, and 85% occur in those younger than 10 years.

In utero detection has been described. They may be discovered at birth. They account for approximately 40% of pediatric tumors that are present within the patient's first 60 days of life.

Overall, a 4:1 preponderance of choroid plexus papillomas to carcinomas is seen.

No distribution by race has been described.

They have been associated with von Hippel-Lindau syndrome, the Li-Fraumeni cancer syndrome (an autosomal dominant syndrome characterized by a mutation in the TP53 gene), and the Aicardi syndrome.

One theory of the etiology  involves the presence of simian vacuolating virus No. 40 (SV40)–related viral DNA.

Pathology:

They may arise wherever a choroid plexus exists.

Tumoral distribution varies between pediatric and adult patients. In children, most CPPs (80%) are located in the lateral ventricles. About 16% of papillomas are found in the fourth ventricle, and 4% are found in the third ventricle. In those aged 0-10 years, the relative incidence of third ventricular papillomas approaches 30%.

The fourth ventricle is the most common location of CPPs in adults.

CPPs occasionally can be bilateral or multiple.

Interventricular extension can occur with a CPP, unlike other interventricular tumors. Although uncommon, interventricular extension through the foramen of Munro, cerebral aqueduct, or foramen of Luschka of Magendie is a helpful diagnostic sign.

CPPs can arise in the cerebellopontine angle, secondary to direct extension from tufts of choroid protruding through the foramen of Luschka. Extension into the foramen magnum may occur, with possible brainstem compression.

Grossly, these tumors are dark red in color with a globular outer surface and an even, gritty cut surface, the latter owing to calcification. They are often are associated with a vascular stalk connected to the choroid plexus, allowing mobility within the ventricular system.

Malignant evolution may occur, with an incidence of 10-30%. The lateral ventricles are the most common sites for malignant degeneration. With a clinical and histologic pattern of malignancy, which is characterized by invasion, mitotic figures, nuclear pleomorphism, necrosis, and metastasis, these tumors are classified as carcinomas. The carcinomas display an infiltrative pattern with features of malignancy. In contrast, papillomas are more homogenous.

As with most CNS neoplasms, confinement to the intracranial cavity is usual.

While the choroid plexus epithelium originates from the primitive medullary epithelium and therefore is related embryologically to ependyma in both structure and function, it is very different from the ependymal cells.  It is more closely akin, morphologically, to the surface epithelia that from the mucosal linings in the other parts of the body.

Seeding can occur throughout the cerebrospinal axis; this usually results in a solitary metastasis from a lateral ventricular tumor in a child and in subarachnoid seeding to the spine from a fourth ventricular lesion in an adult.

On rare occasions, widespread metastases from benign papillomas are observed.

A few cases of papillomas of an nonventricular origin are reported. These are possibly explained by an origin in the embryonic rests of choroid plexus.

Clinical features:

Reports suggest that the median duration of symptoms was 1 month, and approximately one third of patients presented within 2 weeks. The tumor's presence often is heralded by nonspecific signs and symptoms of increased intracranial pressure, which is present in 91% of patients, frequently in association with hydrocephalus due to CSF pathway obstruction, CSF over production, CSF malabsorption due to hemorrhage or deposition of proteinaceous tumor material into the CSF..

Vomiting is the most common sign in children. The presentation can also include hemiparesis, homonymous visual field defects, and generalized tonic/clonic and focal seizures.

When the neoplasm arises within the cerebellopontine angle, the presentation usually involves ataxia and cranial nerve palsy, most commonly that of cranial nerves V, VII, or VIII.

In adults, headache is the most common presenting symptom; this finding may be related to an alteration in head position.

Sudden death  can occur in the third ventriclar tumor, causing acute ventricular obstruction. Spontaneous hemorrhage may be the presenting symptom occasionally.

The disease burden can be significant, especially in young children. Morbidity is associated with developmental delay in 39% of pediatric patients, severe behavioral problems in 17%, and epilepsy in 48%.

Imaging:

Invasion of adjacent neural tissues, and irregular margins suggest carcinoma.

Differential diagnosis include papillary ependymoma, metastasis, meningioma, and pilocytic astrocytoma.

If symptoms suggest, dissemination into the spinal canal should be considered and neuroaxis imaging should be carried out.

At angiography, enlargement of choroid arteries and multiple small tortuous vessels in the arterial phase are characteristic. In the capillary and venous phases, strong homogeneous accumulation of contrast medium in the tumor is seen.

Management:

As a result of their benign nature and slow growth, CPPs are amenable to complete surgical excision, with an expectation of total cure. Not surprisingly, a favorable long-term outcome is expected; the goals are a cure for all children and no requirement for adjuvant therapy.

Despite advances in modern surgical techniques, such as the use of surgical microscopes, bipolar coagulation, stereotaxy, and image-guidance techniques, a significant risk of mortality and morbidity may be associated with surgical treatment.

Extreme tumor vascularity, which is often present, may hinder complete resection.

The perioperative management of hydrocephalus, which is common in patients with CPP, is controversial; subdural fluid collections, frequently caused by the persistence of a ventriculosubdural fistula, are often found in the postoperative period; occasionally, these can cause symptoms of increased intracranial pressure.

Increasingly widespread use of endoscopic surgery may alter the future therapy of choroid plexus neoplasms.

Radiation in children is controversial. Careful follow ups in children with choroid plexus papilloma was suggested by some in the past. It is now generally agreed that surgical resection is the best option.

Radiation therapy after surgical intervention usually is reserved for the treatment of choroid plexus carcinoma.

Chemotherapy has no reported benefit.

Prognosis:

Reports suggest that the 5-year survival rate was 100%, and that tumors do not recur in half of the patients who underwent subtotal resection. If the tumor evolves into malignancy, the prognosis is dismal, with a 5-year survival rate of 26%. However, the histologic appearance may not be predictive of biologic behavior because some highly anaplastic choroid plexus tumors can be clinically benign, whereas some histologically inactive tumors are invasive.

The presence of mitotic figures, although rare in CPP, may be predictive of the likelihood of both recurrence and malignant evolution. Such histologic findings in the surgical specimen should result in close clinical follow-up care of patients, especially in those whose postoperative images show findings of residual tumor.

The evaluation of atypical papillomas, or of more widespread, benign appearing papillomas, may be aided by evaluation of the proliferation index or by presence or absence of various tumor markers. Patients with choroids plexus papillomas with a higher proliferation index or the presence of certain markers have been shown to have worse outcomes, generally observed as tumor recurrence.