Papillary glioneuronal tumor.

Tumors of mixed glioneuronal type are well recognized in the central nervous system. The most common examples of these lesions include gangliogliomas and dysembryoplastic neuroepithelial tumors. Recently, unusual examples of these lesions have been described, including the papillary glioneuronal tumor. This report describes a histologically similar-appearing lesion arising in the left parieto-occipital lobe of an 18-year-old man who presented with headaches and difficulties with vision. Imaging studies noted a large cystic neoplasm marked by a peripheral rim of enhancement. The patient underwent gross total resection of the tumor, which histologically was marked by a mixture of glial (glial fibrillary acidic protein-positive) and neural (synaptophysin-positive) components. Architecturally, the tumor was notable for a focal pseudopapillary pattern. Papillae were lined by predominantly glial cells, with intervening areas occupied by neurally differentiated cells. Mitotic activity, vascular proliferation, and necrosis were not noted. A MIB-1 labeling index of 1.1% was seen. p53 immunoreactivity was not observed. This report adds further evidence supporting the existence of this unusual mixed glioneuronal tumor of the central nervous system.