Ultrastructure of three choroid plexus papillomas

This report describes the ultrastructure of three choroid plexus papillomas (CPP) from female patients, aged 2 months, 3 years, and 57 years, respectively. The infantile case manifested clinical evidence of excess CSF formation. All three were well-differentiated neoplasms resembling normal choroid plexus (CP). Each displayed distinctive individual patterns of plasmalemmas, organelle population, and nuclei. The two childhood tumors contained prominent deposits of cytoplasmic glycogen, thus simulating the embryonic state. The vasculature of all three lesions included fenestrated capillaries indistinguishable from those of normal CP. Ventricular plasmalemmas were separated from lateral and basal plasmalemmas by tight junctions. The geometrical relationship between capillaries, tumor cells, and ventricle was characteristic of epithelia involved in fluid transport. These findings offer structural evidence that well-differentiated CPPs are capable of participating in CSF formation.