multinodular and vacuolating neuronal tumour (MVNT)

Multinodular and vacuolating neuronal tumors (MVNT) are a newly recognized cytoarchitectural pattern in the recently revised 2016 edition of the WHO classification of CNS tumors.

Radiologically, MVNTs appear as small 'bubbly' indolent subcortical tumors that sometimes present with seizures. These tumors have been most frequently identified in the temporal lobe, although that is likely to be due to that location being more likely to result in seizures than necessarily a predilection for that lobe .

Epidemiology

The true epidemiology of these tumors is unknown as they have only been recently described and many are asymptomatic and thus likely undiagnosed (or misdiagnosed). Reported cases are mostly in young to middle-aged individuals with adult-onset epilepsy .

Clinical presentation

Many of these lesions are probably asymptomatic and may be found incidentally on imaging for other reasons, and have, over the year, been misinterpreted a variety of other lesions (see differential diagnosis below). In some individuals these tumors are epileptogenic.

Pathology

Although currently considered a tumor and a growth pattern of gangliocytomas (WHO grade I), it is possible that MVNTs are closer to developmental abnormalities than true tumors .

Histopathologic hallmark of MVNT consists of neuroepithelial cells with conspicuous stromal vacuolation arranged in nodules principally within the deep cortical ribbon and superficial subcortical white matter . Immunostaining is positive for synaptophysin, HuC/HuD neuronal antigens and p62 but were negative for other markers (e.g. IDH1, nestin, NeuN, neurofilament, GFAP, and CD34) .

Radiographic features

CT

Smaller lesions are difficult to identify, but if seen will appear as non-enhancing low attenuation lesions deep to the cortex in the subcortical white matter.

MRI

These tumors appear as a cluster of well-circumscribed high T2 signal 'bubbles' located predominantly in the subcortical white matter but can involve the overlying cortex .

• T1: hypointense to adjacent gray and white matter
• T1 C+:
  • usually no enhancement
  • some faint focal enhancement may be seen
• T2: hyperintense to grey and white matter, almost as high as CSF
• FLAIR: do not suppress

Treatment and prognosis

MVNTs appear to be benign tumors with very indolent biological behavior which can, if asymptomatic, be followed by imaging alone. In symptomatic patients (epileptic) surgical resection often controls seizures, with no tumor regrowth reported .

Differential diagnosis

Possible considerations include

• dysembryoplastic-neuroepithelial-tumor - DNET
  • can appear similar but usually is mostly cortical (rather than subcortical)
  • often has bright FLAIR rim
• focal cortical dysplasia (type II) 
  • high T2 signal deep to the cortex is in the same location but is usually associated with a radial glial band (transmantle sign) and with thickened abnormal overlying cortex
• perivascular spaces
  • location can be similar
  • usually more elongated along vessel long axis
  • fully attenuating on FLAIR

Siehe auch:

• Dysembryoplastischer neuroepithelialer Tumor
• hippocampale Sulcusreste
• T2-hyperintense subkortikale Läsionen
• blasige subkortikale T2-hyperintense Läsionen