Pathology of choroid plexus papillomas: a review

Choroid plexus papillomas (CPPs) are rare, usually slow growing neoplasms. Their biological behaviour cannot be predicted in an individual case. Furthermore, the neuropathological diagnosis of these neoplasms is occasionally difficult because light and electron microscopical and immunohistochemical features may overlap with those of other neoplasms localising in the choroid plexus. The aim of this paper is to review the pathological literature (light and electron microscopy (EM) and immunocytochemistry), to provide guidance on current diagnostic tools and criteria and address the identification of 'atypical' CPPs, e.g. those CPPs with histological features indicative of aggressive behaviour, in an attempt to help bridge the diagnostic gap between benign CPPs on the one hand and choroid plexus carcinomas (CPCs) on the other.