Focal glial differentiation and oncocytic transformation in choroid plexus papilloma.

The histiopathological features of a choroid plexus papilloma in a 27-year-old male are described. The tumor displayed marked oncocytic transformation and glial differentiation of the epithelium in areas in which there was also marked sclerosis of the fibrovascular cores. Non-membrane-bound bodies of intermediate filaments characterized ultrastructurally the cells with glial differentiation.