Newly recognised Tumour Types in Glioneuronal tumours according to the 5th edition of the CNS WHO Classification

Abstract

Glioneuronal tumours (GNT) are uncommon neoplasms, characterised by glial and neuronal differentiation.

In the 5th edition of the World Health Organization (WHO) Classification, they are grouped under the heading "Glioneuronal and neuronal tumours", which comprises fourteen different tumours, among which the diffuse glioneuronal tumour with oligodendroglioma-like cells and nuclear clusters (DGONC), myxoyd glioneuronal tumour (MGT) and multinodular and vacuolating neuronal tumour (MNVNT) are new types.

MGT and MNVNT are classified WHO grade 1 and may be recognised and diagnosed by peculiar clinical-pathological features. DGONC was not assigned a WHO grade and was only provisionally included among GNT, due to the possibility that it rather represents an embryonal tumour type or subtype. Although the histopathological characteristics may be useful for its identification, the specific methylation profile is an essential diagnostic criterion for DGONC.

Keywords: diffuse glioneuronal tumour with oligodendroglioma-like cells and nuclear clusters; glioneuronal tumours; multinodular and vacuolating neuronal tumour; myxoyd glioneuronal tumour.

Figure 1.

Diffuse glioneuronal tumour with oligodendroglioma-like features and nuclear clusters. (A) The tumour is mildly cellular, composed of medium-size cells with mild pleomorphic oval nuclei along with cells with round nuclei and clear perinuclear halo (H&E, 200X magnification). (B) Multinucleated cells and nuclear clusters composed of large pleomorphic nuclei (H&E, 400X magnification). (C) Olig2 immunostain shows a diffuse nuclear positivity (100X magnification). (D) Neoplastic cells are reactive for Synaptophysin antibody (100X magnification)

Figure 2.

Myxoid glioneuronal tumour. (A) Sagittal and (B) Axial T2-weight MRI. Hyperintense lesion in the anterior portion of the septum pelluciduum resulting in a biventricular hydrocephalus. (C) Histological evaluation shows a tumour characterized by proliferation of oligodendrocyte-like cells embedded in a prominent myxoid stroma, with a delicate capillary network (H&E, 100X magnification). (D) NeuN antibody highlights occasional floating neurons (400X magnification).

Figure 3.

Multinodular and vacuolating neuronal tumour. (A) MRI demonstrates FLAIR-hyperintense clustered nodular lesion, with involvement of cortex and superficial white matter, and absence of mass effect. (B) High-power magnification highlights prominent vacuolar changes and mature-appearing neuronal cells of intermediate to large size (H&E, 200X magnification). (C) Synaptophysin is only weakly and focally expressed (200X magnification).