Choroid Plexus Papillomas
Choroid plexus papillomas are benign neoplastic growths that arise from the ventricular choroid plexus and can be considered of ependymal origin. They are slow-growing. They remain asymptomatic for considerable periods, are commonly associated with hydrocephaJus, and are liable to hemorrhage spontaneously.
Considering adults and children together! choroid plexus papillomas are rare, constituting less than 1 percent of all primary intracranial tumors. Although they occur at any age, the majority occur in the first decade; thus in children they constitute 3 percent of intracranial neoplasms. Forty eight percent of those reported in the literature were in children under 10 years of age and 20 percent in infants under 1 year of age. They are among the more frequent tumors in children under the age of 3 years.
The tumor affects both sexes equally, and genetic factors do not seem to plays a role.
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In adults, the choroid plexus papilloma is most often located in the fourth ventricle, whereas in children it usually arises in the lateral ventricles, the left more commonly than the right. The third ventricle is seldom involved.
In gross examination the tumor is a dark pink or red meaty mass with an irregular papillary surface. In the lateral ventricle it is accompanied by a considerable enlargement of the ventricle. If it is located in the lateral recess of the fourth ventricle, it can significantly distort surrounding structures. It is characteristically easy to separate from the surrounding brain. Small foci of hemorrhage may be present in its interior.
Typical of the choroid plexus papilloma in microscopic examination is its resemblance to the normal choroid plexus. Resting on a slender vascular connective tissue stroma is a delicate arrangement of papillary formations, of usually single layer of cuboidal or columnar epithelium. Cilia and blepharoplasts are found in some infantile tumors. Malignant changes indicate that the tumor is the rare choroid plexus carcinoma, representing an entirely different clinical condition than the choroid plexus papilloma
On occasion gross and microscopic spread in the leptomeninges of a benign choroid plexus papilloma is seen at postmortem examination. In these cases there are no malignant histological changes and such lesions do not cause clinical symptoms.
In the differential histological diagnosis papillary ependymoma and xanohogranuloma of the choroid plexus must be considered. In the former the cells are usually piled up in multiple layers and the stromal support is neuroglial, not connective tissue. The latter consists of small lesions yellowish and firm, with deposition of cholesterol in their stroma; they are often bilateral.
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Ventricular enlargement is seen in association with most but not all choroid plexus papillomas This may be due to a combination of factors: overproduction of CSE, obstruction of CSF pathways by the tumor mass, or subarachnoid scarring due to recurrent bleeding from the tumor.
In those tumors located in the fourth and third ventricles the tumor may reach a size that can obstruct CSF flow. In these cases removal of the tumor mass may resolve the hydrocephalus.
Recurrent occult bleeding is a known complication of these tumors, and the subarachnoid obstruction due to basal meningitis and fibrosis may then lead to hydrocephalus, thus accounting to the lack of resolution of the hydrocephalus despite tumor removal in some cases
Overproduction of CSF by the tumor mass has long been suspected and was thought to be documented in two patients. In one of these, measurement of CSF production by ventriculo-lumbar perfusion revealed a formation rate of 1.05 ml/min prior to surgical removal of the tumor; 8 weeks after surgery it was measured at 0.2 ml/min. This may explain the resolution of hydrocephalus in some cases after the removal of a choroid plexus papilloma from the lateral ventricle.
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