Choroid plexus papillomas of the posterior fossa: extraventricular extension, intraventricular and primary extraventricular location. Report of four cases.

Four cases of Choroid Plexus Papilloma (CPP) of the posterior fossa are presented. Two cases had extraventricular extension from the fourth ventricle to the Cerebellopontine Angle (CPA) through the foramen of Luschka, in one the CPP was located primarily in the CPA and the fourth case was only in the fourth ventricle. CPP are rare tumours of the Central Nervous System and primary extraventricular location is extremely rare. We know that primary location in the extraventricular and intraventricular regions and extraventricular extension have different pathological mechanisms. The main purpose of this paper is to discuss and review some possible explanations for these mechanisms.