Multinodular and vacuolating neuronal tumor
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 1-4.
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 1-4.
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.
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 5.
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 1-3. 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) 1-4.
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.
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 1,3,4.
- T1: hypointense to adjacent gray and white matter
- usually no enhancement
- some faint focal enhancement may be seen 3,4
- 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 1-4.
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
- location can be similar
- usually more elongated along vessel long axis
- fully attenuating on FLAIR
- 1. Bodi I, Curran O, Selway R et-al. Two cases of multinodular and vacuolating neuronal tumour. Acta Neuropathol Commun. 2014;2 (1): 7. doi:10.1186/2051-5960-2-7 - Free text at pubmed - Pubmed citation
- 2. Fukushima S, Yoshida A, Narita Y et-al. Multinodular and vacuolating neuronal tumor of the cerebrum. Brain Tumor Pathol. 2015;32 (2): 131-6. doi:10.1007/s10014-014-0198-9 - Pubmed citation
- 3. Huse JT, Edgar M, Halliday J et-al. Multinodular and vacuolating neuronal tumors of the cerebrum: 10 cases of a distinctive seizure-associated lesion. Brain Pathol. 2013;23 (5): 515-24. doi:10.1111/bpa.12035 - Pubmed citation
- 4. R.H. Nunes, C.C. Hsu, A.J. da Rocha, et al. Multinodular and Vacuolating Neuronal Tumor of the Cerebrum: A New “Leave Me Alone” Lesion with a Characteristic Imaging Pattern. (2017) American Journal of Neuroradiology. 38 (10): 1899. doi:10.3174/ajnr.A5281 - Pubmed
- 5. Maria Thom, Joan Liu, Anika Bongaarts, et al. Multinodular and vacuolating neuronal tumors in epilepsy: dysplasia or neoplasia?. (2018) Brain Pathology. 28 (2): 155. doi:10.1111/bpa.12555 - Pubmed
- 6. Reema Alsufayan, Paula Alcaide-Leon, Lyne Noel de Tilly, et al. Natural history of lesions with the MR imaging appearance of multinodular and vacuolating neuronal tumor. (2017) Neuroradiology. 59 (9): 873. doi:10.1007/s00234-017-1884-1 - Pubmed