Papillary glioneuronal tumor.

Papillary glioneuronal tumor (PGNT) is a rare, recently recognized tumor type histologically characterized by pseudopapillary architecture associated with compact areas composed of neuronal elements in different maturation states. The histogenesis of this tumor type is still unclear. The immunophenotype of PGNT comprises expression of several glial and neuronal proteins. Recently, immunohistochemical expression of Olig2 in a fraction of tumor cells has been reported, suggesting an additional oligodendroglial or at least oligodendroglia-like tumor cell component. We report a further case of papillary glioneuronal tumor in a 12-year-old boy with immunohistochemical expression of PDGFRalpha, Olig2 and Nestin in support of a postulated origin of this tumor type from common progenitor cells in the subependymal plate. Nevertheless, further studies are needed to clarify the histogenesis of PGNT.