Ultrastructure of disseminated choroid plexus papilloma.

A disseminated choroid plexus papilloma (DCPP) with a malignant change in the cervico-spinal leptomeninges observed 4 years after the removal of choroid plexus papilloma (CPP), originating from the fourth ventricle, was studied under the electron microscope. Although the ultrastructure of intracranial CPP has been reported by several authors, there are just a few reports on DCPP. The present tumor was ultrastructurally very similar to normal choroid plexus, but the lack of the capillary fenestration and of invaginations of the epithelial basal plasmalemmas suggested that the epithelium was deprived of secretory function.