Membrane Structures Between Craniopharyngioma and the Third Ventricle Floor Based on the QST Classification and Its Significance: A Pathological Study

The aim of this study was to clarify the relationship between craniopharyngiomas (CP) and the third ventricle floor by analyzing the membranes between them. Eight fetal specimens were first examined by hematoxylin and eosin and immunofluorescence staining to determine optimal markers for identifying membrane structures in the sellar region. Then, 17 CP with third ventricle floor involvement that had been removed by total en bloc resection through a transsphenoidal approach were examined. We found that the dura mater, arachnoid membrane, and pia mater could be seen to separate type Q tumors from the third ventricle floor. The arachnoid membrane and pia mater could be seen between type S tumors and the third ventricle floor. Pia mater could be seen between type T tumors and the third ventricle floor; however, at the origin point of the tumor, pia mater could be loosened or replaced by the tumor. Although some type T tumors compressed the third ventricle, the ependymal layer remained intact. Based on these embryonic and pathological data, we suggest that CP are nonneuroepithelial, epi-pia mater, and epi-third ventricle tumors.