Papillary glioneuronal tumor

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Papillary glioneuronal tumors are rare well circumscribed complex solid cystic supratentorial lesion with an indolent clinical course.

Epidemiology

These tumors typically are diagnosed in younger patients (median age at diagnosis 23 years) but are reported essentially in all ages . No sex predilection has been identified .

Clinical presentation

Clinical presentation is non-specific, primarily comprising seizures and/or headaches. Focal neurological deficits may also be present.

Pathology

Papillary glioneuronal tumors were first recognized in the 2007 edition of the WHO classification of CNS tumors and are considered WHO grade I tumors.

The majority of these tumors are in the cerebral hemispheres, with occasional intraventricular tumors described .

Macroscopic appearance

These tumors usually demonstrate a mixture of solid and cystic components, sometimes with calcification .

Microscopic appearance

Papillary glioneuronal tumors contain both glial (astrocytic) and neural elements. Characteristic microscopic features are hyalinized vascular pseudopapillary architecture with a pseudostratified layer of cuboidal glial cells and focal collections of neurocytes and ganglion cells.

Immunophenotype

Immunohistochemistry of the cuboidal glial cells reflects their glial appearance :

  • GFAP: positive
  • S100: positive
  • nestin: positive

In contrast, the neuronal components show a separate immunophenotype :

These tumors demonstrate a low Ki-67 proliferation index/MIB-1 index ~1-2% . Rarely, tumors with higher mitotic index are encountered and some have more aggressive behavior .

Radiographic features

Features on imaging are very similar to ganglioglioma. They are supratentorial solid-cystic or cystic with solid nodule lesions showing intense but heterogeneous enhancement. Calcification is a frequent finding . Hemorrhage is seen in ~10% of cases and is sometimes very pronounced .

MRI
  • T1: isointense to hypointense 
  • T2: inhomogeneously hyperintense
  • FLAIR:
    • inhomogeneously hyperintense nodule
    • cystic components may suppress
  • T1 C+: avid but heterogeneous enhancement of the solid nodule 

Treatment and prognosis

Papillary glioneuronal tumors are indolent and surgical resection is usually sufficient to effect a cure. In cases where proliferation is high (e.g. Ki-67 >5%) then local recurrence has been described .

Differential diagnosis

The differential diagnosis is primarily of other parenchymal tumors with mixed solid and cystic components, including: