Papillary glioneuronal tumor--contribution to a new tumor entity and literature review.

Papillary glioneuronal tumor (PGNT) is a recently identified low-grade mixed glial-neuronal neoplasm of juvenile and young adult patients. The WHO classification does not categorize this tumor as a separate entity, but rather considers it as a variant of ganglioglioma. We present a new case of this rare entity, representing the 3rd case of this lesion in Chinese patients and review the findings in 34 patients from different case reports found in the international literature. This report describes a histologically similar-appearing lesion arising in the left frontoparietal lobe of a 23-year-old man. Its salient morphological characteristics are the presence of pseudopapillary structures composed of blood vessels, often hyalinized, lined by uniform small astrocytes and a proliferation of neurocytic cells which eventually admixed with ganglioid and ganglion cells. Sporadic Rosenthal fibers, foci of calcification, areas of hemosiderin deposition were identified. The mean Ki67 labeling index remained below 1%. Signs of anaplasia, in particular mitotic figures, endothelial proliferation or necrosis were consistently lacking. It is important that every new case of PGNT is reported to allow its recognition and classification. We perceive PGNT as a clinically and morphologically well-delineated subgroup of extraventricular low malignant potential neoplasm, whose presentation may allow for consideration as an entity.