Choroid plexus papillomas and human choroid plexus

Choroid plexus papillomas and mature human choroid plexus were studied by light and electron microscopic techniques. The mature choroid plexus has three types of cells: Type I cells are cuboidal or columnar cells and line the villi; Type II cells are flat cells lining connective tissue adjacent to neural tissue; and Type III cells are flat cells lining crypts in connective tissue. The cells of benign papillomas were similar to the fully developed Type I cells. The cells of a malignant papilloma were similar to the underdeveloped-appearing Type III cells. A variant malignant papilloma had well differentiated mucus-secreting cells resembling goblet cells.