[So-called "ependymoma of the foramen of Monro" with differentiation of tissue toward the subfornical organ].

A tumour was found in the left ventricle of a 25 year-old woman. Histology of this "ependymoma of Monro's foramen" shows characteristic structures of the subfornical organ. Whereas tumours of the pituitary or the pineal gland, which are also part of the circumventricular organs, are quite frequent, a tumour with differentiation characteristic of the subfornical organ is a rarity.