Choroid plexus papillomas and human choroid plexus. A light and electron microscopic study.

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.