Papillary glioneuronal tumor: a new entity awaiting inclusion in WHO classification
© Radotra et al; licensee BioMed Central Ltd. 2007
Received: 19 December 2006
Accepted: 08 February 2007
Published: 08 February 2007
Papillary glioneuronal tumor (PGNT) is a recently described lesion of the brain, which is still not included as a separate entity in WHO classification. To date 32 cases of PGNT have been reported in the world literature. We report the 33rd case, a 41-year-old male who presented with pain in the nape of the neck. MRI showed a large, predominantly solid mass involving the cerebral parenchyma of the left temporal and parieto-occipital lobes with extension across the midline. Histologically, it was a mixture of glial and neuronal components. Architecturally, the tumor was notable for its pseudopapillary pattern with hyalinized vessels. PGNT is considered as a low grade neoplasm and surgical excision has been curative in most of the cases. More cases of PGNT need to be reported as they may add further knowledge about its biologic behavior and allow its recognition and classification.
Tumors of mixed glioneuronal type like gangliocytoma, dysembryoplastic neuroepithelial tumor, ganglioglioma, anaplastic ganglioglioma and central neurocytoma are well recognized in the central nervous system . In the year 1998 a new variant of mixed glioneuronal tumor was described by Komori et al.  which is still not included as a separate entity in the WHO classification. It was composed primarily of glioneuronal elements with prominent pseudopapillary structures. This unusual mixed glioneuronal tumor of the central nervous system was called papillary glioneuronal tumor (PGNT). The pseudopapillae are usually composed of hyalinized vessels covered by a single or stratified layer of glial fibrillary acid protein (GFAP) positive astrocytes. The cells forming neuronal elements include neurocytes, ganglioid cells or ganglion cells within the neuropil which are synaptophysin positive. To date 32 cases of PGNT have been reported in the world literature. We report the 33rd case with a review of the literature.
The presence of angiomatous areas consisting of closely placed smaller and thin walled vessels (Figure 2d) was a unique finding in the present case. These vessels were lined by single layer of endothelial cells with absence of smooth muscle in their wall. These angiomatous areas occupied about one third of the total tumor tissue. In addition a focus of myxoid change was also seen but there were no mature neuronal or ganglionic cells, true or pseudo-rosettes. Mitosis, necrosis and vascular endothelial proliferation were absent.
The PGNT is a low grade neoplasm distinct from previously described variants of mixed glioneuronal tumors because of the prominent pseudopapillary architecture and unique clinical and radiographic features. Analysis of all the reported cases in the literature suggests that this tumor has no sex predilection and can affect any age group (range 4–75 years; mean 28 years) [3, 4]. Seizures are most common and typify temporal lobe tumors, whereas lesions at other sites usually feature headache and nonspecific signs and symptoms. No focal deficits have been reported so far. Occasionally the patient may be asymptomatic [2, 6]. The index case is unusual in the sense that there was no history of seizures despite the temporal location of the tumor. Radiologically it is almost always a cystic lesion, usually with a mural nodule. Size of the tumor may range from 1 cm to 7 cm (mean, 4.6 cm) . The present case differs radiologically from the prior reports in presenting without any obvious cystic change and crossing the midline.
Pathological features of Papillary glioneuronal tumor
Number (n = 33)
Cystic with mural nodule
Biphasic (glial & neural)
Pigment laden macrophages
Mild lymphocytic infiltrate
Differential diagnostic considerations include other neoplasms that may radiologically present as cystic masses with a variably enhancing mural nodule, such as pilocytic astrocytoma and ganglioglioma. The architectural similarities have been noted between PGNT, central neurocytoma and ganglioglioma, however its geographic limitation to the cerebrum suggests a different histogenesis. Other differential diagnoses include ependymoma, extraventricular neurocytic neoplasm and dysembryoplastic neuroepithelial tumor.
Treatment offered to these patients is surgical resection and, if necessary, post operative radio- or chemo-radiotherapy. Follow-up data range from 6 months  to 19 years  and recurrence has been reported in only one case . All the tumors described had only moderate cellularity. Mitosis, necrosis and endothelial proliferation were not seen in any of the cases. MIB-1 labeling index has also been found to be low (0.5%–2.5%, mean 1.3%) [2, 4, 7]. The presence of pseudopapillae, degenerative changes and low MIB-1 labeling index all indicate that PGNTs are generally slow growing and low grade neoplasms and thus, appear to carry a good prognosis. Since there has been a rapid increase in the number of reported cases of PGNT, this entity should be included as a separate category in the WHO classification. This would facilitate its wider recognition and help establish an evidence-based approach to treatment.
In conclusion, we report a rare brain tumor, the PGNT in a 41-year-old male with bilateral involvement without any obvious cystic change. On microscopy there was extensive angiomatous change. To the best of our knowledge these changes have not been reported previously.
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