Choroid plexus papilloma, light micrograph. Choroid plexus tumours comprise爈ess than 1% of all brain tumours. Almost?0% of cases occur in children爉aking up?% to 4% of pediatric brain tumours. The most common location is爈ateral ventricles. Given their location, the presenting symptoms and signs are related to爃ydrocephalus燼nd爄ncreased intracranial pressure. Choroid plexus papillomas are燾ircumscribed, papillary masses燾onsisting of爌seudostratified epithelial cells lining fibrovascular cores燼s seen in this low power image. They closely resemble normal choroid plexus, however, they are more cellular and exuberant and lack the surface hobnailing of the normal choroid plexus. The燾ytologic atypia is minimal or absent and mitotic activity is not increased.