Chordoid glioma of the third ventricle: four cases including one case with papillary features.

Chordoid glioma is a rare, slowly growing tumor of the CNS, which is always located in the third ventricle of adults. Chordoid glioma has classic histological features consisting of clusters and cords of epithelioid tumor cells embedded within a mucinous stroma with rich lymphoplasmacytic infiltrate. The important distinctive immunohistochemical feature of this neoplasm is strong and diffuse reactivity for GFAP. Here, we report four cases of chordoid glioma that occupied the anterior portion of the third ventricle or suprasellar region. These four cases were all adult females with almost typical clinical, radiological, histologic and immunohistochemical characteristics of chordoid glioma. However, in one case there was an unusual histologic finding with regard to the papillary region. In this region, elongated tumor cells were observed radiating toward a central vessel to form characteristic papillary structures. Immunohistochemically, three cases showed strong reactivity for GFAP, and one exhibited weak reactivity. All cases were focally positive for epithelial membrane antigen, CD34 and D2-40, but negative for neurofilament protein (NFP). Several ultrastructural investigations have supported the ependymal origin of chordoid glioma. In some cases of immunoreactivity for NFP, some authors have supposed that chordoid glioma originates from a multipotential stem cell with glial and neuronal cell differentiation. With regard to the present four cases with immunoreactivity for D2-40 (an ependymal marker) and CD34 (undifferentiated neural precursors) and based on previously published data, we considered that the majority of chordoid gliomas had an ependymal origin, and that a small minority might have originated from a multipotential stem cell having ependymal and neuronal cell differentiation.