Papillary glioneuronal tumor--a new variant of benign mixed brain neoplasm.

We report a case of a 14-year-old girl with papillary glioneuronal tumor (PGNT) in right parietal lobe. On MRI the tumor presented as a contrast enhancing mass with small central hypodense area and consisted of areas similar to central neurocytoma intermixed with vessels surrounded with glial cells. There were also small loose areas superficially reminding DNT. Neurocytic component presented strong synaptophysin immunostaining, while intermixed glial element presented GFAP-immunopositivity. Our case is similar to previously reported PGNT, but an important difference lies in not distinct cystic formation and a presence of loose, edematous tissue. PGNT may be regarded as a variant of ganglioglioma or as a complex variant of extraventricular neurocytoma and belongs to a wide group of benign, dysembryoplastic or even hamartomatous neuroepithelial tumors, which may differentiate into both, glial or neuronal direction: pleomorphic astrocytoma may posses neurocytic differentiation, desmoplastic infantile ganglioglioma may be regarded as complex superficial dural astrocytoma and DNT may present gliomatous areas (complex DNT). Also other rare tumors reminding DNT have been reported: DNT-like neoplasm of septum pellucidum and rosetted glioneuronal tumor. From this point of view it is important to remember that such a wide spectrum may be difficult to discriminate into very narrow clinico-pathological entities.