Papillary glioneuronal tumor: not always a benign tumor?

Papillary glioneuronal tumor (PGNT) is a variant of ganglioglioma, characterized by a pseudopapillary structure with a single pseudostratified layer of small, cuboidal, GFAP-positive cells around hyalinized blood vessels. To date, less than 30 cases have been described with a usually benign course. We report two additional cases: a clinically, radiologically and histopathologically typical tumor in a 38-year-old man and an atypical tumor with histopathological features of anaplasia in a 74-year-old woman. The latter tumor showed the classical pseudopapillary pattern with ganglioid cells and some astrocytes between the papillae, but also had changes suggestive of anaplasia including necrosis, capillary endothelial proliferation, mitoses, dedifferentiation with loss of GFAP expression of the cuboidal cells and increased Ki-67 labeling of over 10%. Only one other case with increased proliferative activity in a minigemistocytic component has previously been described. Our cases indicate that PGNT type of ganglioglioma can have a spectrum of anaplastic changes of higher grade.