Craniopharyngioma: Craniopharyngiomas arise along the infundibular stalk, and are thought to be of developmental origin. They are usually very slow growing tumors, and cause symptoms by compressing the hypophysis, optic structures and the third ventricle. There are frequently solid portions and cystic portions. In this specimen the cystic portion of the neoplasm extends upward into the third ventricle. The third ventricle is dilated. When the third ventricle is widened in this fashion, inevitably the adjacent structures within hypothalamus and thalamus are affected.