Colloid cyst of the third cerebral ventricle with an embryological remnant consistent with paraphysis cerebri in an adult human.

The histogenesis of colloid cysts of the third ventricle remains unsettled. Initial theories favored a neuroepithelial (paraphysis, ependyma, choroid plexus) origin and some investigators based on morphologic analysis have offered an alternative endodermal source. We report a case of colloid cyst of the third ventricle arising in association with a remnant which we believe corresponds to the paraphysis cerebri in man.