Central neurocytomas are WHO grade 2 neuroepithelial intraventricular tumors with fairly characteristic imaging features, appearing as heterogeneous masses of variable size and enhancement within the lateral ventricle, typically attached to the septum pellucidum. They are typically seen in young patients and generally have a good prognosis provided a complete resection can be achieved.
Extraventricular neurocytomas (previously known as cerebral neurocytomas) are very uncommon, considered distinct entity and are therefore discussed in a separate article.
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Epidemiology
Central neurocytomas are typically seen in young patients (70% diagnosed between 20 and 40 years of age) and account for less than 1% (0.25-0.5%) of intracranial tumors 10,11. There is no reported gender predilection 10.
Clinical presentation
Typically, central neurocytomas present with symptoms of increased intracranial pressure, headaches being most frequent, or seizures (especially tumors with extraventricular extension).
A relatively short clinical course, typically only a few months, is most common. Rarely central neurocytomas may be associated with sudden death secondary to acute ventricular obstruction 4. Also rare, is a sudden presentation due to intraventricular hemorrhage 7.
Pathology
Central neurocytomas demonstrate neuronal differentiation and histologically appear similar to oligodendrogliomas which, historically, resulted in many tumors erroneously categorized.
The initial description classified them as WHO grade 1 lesions. However, this was upgraded in 1993 to WHO grade 2 as it was recognized that at least some of these tumors exhibited more aggressive behavior 10.
Location
The vast majority of central neurocytomas are located entirely within the ventricles. Typical locations include 4:
lateral ventricles around foramen of Monro (most common): 50%
both lateral and 3rd ventricles: 15%
bilateral: 15%
3rd ventricle in isolation: 5%
Macroscopic features
Central neurocytomas are usually friable grey-colored tumors, sometimes demonstrating areas of calcification and hemorrhage 11.
Microscopic features
The cells are typically uniform and round with a salt and pepper finely speckled chromatin 11. They also demonstrate areas of variable architecture that are reminiscent of other tumors, including oligodendrogliomas, pineocytomas and neuroendocrine tumors 11.
Immunophenotype
Immunohistochemistry confirms the purely neuronal origin by positivity to neuronal markers such as 11:
synaptophysin: positive
NeuN: positive
neuron-specific enolase: positive
MAP2: usually positive
class III beta-tubulin: usually positive
GFAP and IDH-1 R132H are negative 11.
Genetics
Importantly, IDH mutations and 1p19q co-deletion are absent (characteristic of oligodendrogliomas).
Variants
Extraventricular neurocytomas are histologically similar but lack an intraventricular component 11.
Ganglioneurocytoma is a variant, usually of extraventricular neurocytomas, demonstrating a distinct ganglion cells component 6,11,12.
Radiographic features
CT
Central neurocytomas are usually hyperattenuating compared to white matter. Calcification is seen in over half of cases, usually punctate in nature 4,10. Cystic regions are frequently present, especially in larger tumors. Contrast enhancement is usually mild to moderate. Accompanying ventricular dilatation is often present.
MRI
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T1
isointense to grey matter
heterogeneous
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T1 C+
mild-moderate heterogeneous enhancement
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T2/FLAIR
typically iso to somewhat hyperintense compared to brain
numerous cystic areas (bubbly/swiss cheese appearance), many of which completely attenuate on FLAIR
prominent flow voids may be seen 10
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GE/SWI
calcification is common, typically punctate
hemorrhage (especially in larger tumors) is common
uncommonly results in ventricular hemorrhage
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DWI
diffusion restriction of the solid component 13
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MR spectroscopy
may have a strong choline peak 13
glycine peak (3.55ppm) has also been reported 10
Angiography (DSA)
A tumor blush is frequently identified, with the mass supplied by choroidal vessels. No large feeding arteries are usually seen.
Treatment and prognosis
Complete surgical resection is usually curative (5 years survival 81%). When only incomplete resection is possible or extraventricular extension is present, then adjuvant radiotherapy (and sometimes chemotherapy) are added, although their benefit is not well established.
Cases of CSF dissemination have been reported, but are rare 10.
History and etymology
In 1982, Hassoun described central neurocytoma for the first time 2.
Differential diagnosis
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more frequent in childhood
more commonly in 4th ventricle
supratentorial tumors (esp in children) often have a significant extraventricular (parenchymal) component 4
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no contrast enhancement
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homogeneous contrast enhancement
well-circumscribed mass
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typically found in the 4th ventricle
usually older individuals 8
may have ependymoma components and look very similar 9
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subependymal giant cell astrocytoma
in patients with tuberous sclerosis
vivid contrast enhancement
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mainly in children
typically show intense contrast enhancement
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older patients
usually stronger contrast enhancement
history of primary (e.g. renal cell carcinoma)
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thalamic glioblastoma
older patients
surrounding vasogenic edema
less lace-like appearance (if any)
elevated MR perfusion (rCBV)
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this is especially difficult in cases where there is a parenchymal component as histologically the tumors are very similar
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