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Central neurocytoma in the posterior fossa
  1. Pranav Rai,
  2. Raghavendra Nayak,
  3. Debish Anand and
  4. Girish Menon
  1. Neurosurgery, Kasturba Medical College Manipal, Manipal Academy of Higher Education (MAHE), Manipal, Karnataka, India
  1. Correspondence to Dr Raghavendra Nayak, drnayakneuro{at}gmail.com

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Description

Central neurocytomas (CNs) are rare, benign neoplasms arising from a neuronal lineage and account for 0.1%–0.5% of all central nervous system tumours. Typical location of CNs is the lateral ventricle touching the foramen of Munro.1 Occurrence of the tumours in the posterior fossa is extremely rare; till now only seven cases (table 1) have been reported to the best of our knowledge.2

An 8-year-old girl was presented to us with early morning headache and blurring of vision for 1 month and gait instability for 15 days. These symptoms were gradually progressive. Since 3 days, she started having intractable nausea and vomiting. Neurological examinations showed mild papilledema and bilateral sixth nerve paresis, indicating raised intracranial pressure. She had an ataxic gait. CT scan was showing an ill-defined, lobulated, heterogeneously enhancing and hypodense intraventricular lesion arising from the floor of the fourth ventricle. There was no evidence of calcification or haemorrhage within the lesion. MRI demonstrated an inhomogeneous, heterogeneously enhancing vermian mass with few cystic areas with supratentorial obstructive hydrocephalus. Mass was hypointense on T1-weighted sequences and hyperintense in T2-weighted sequences (figure 1). Our differential diagnosis was medulloblastoma, ependymoma or atypical teratoid rhabdoid tumour.

Figure 1

CT scan: (A, B) an ill-defined lobulated heterogeneously enhancing hypodense intraventricular lesion arising from the floor of the fourth ventricle. No evidence of calcification or haemorrhage within the lesion. MRI: a fourth ventricular mass which was (C) hypointense on T1-weighted image, (D) hyperintense on T2-weighted image, (E) hyperintense on fluid-attenuated inversion recovery sequence, and (F) Showing heterogeneous enhancement on giving gadolinium contrast.

The patient underwent a midline suboccipital craniotomy and complete excision of the tumour. Histopathology showed the isomorphic cells with clear cytoplasm, speckled chromatin and fibrillar matrix, suggesting oligodendroglioma or ependymoma. But, immunohistochemical study was positive for synaptophysin and neuron-specific enolase and negative for glial fibrillar acidic protein, suggesting the CN. Histological features were atypical, and the proliferation marker (Ki-67) was 1 (figure 2).

Figure 2

H&E staining showing (A) isomorphic cells with clear cytoplasm, speckled chromatin and fibrillar matrix. (B) Synaptophysin positivity on immunohistochemical study.

CNs were first described by Hassoun et al 3 in 1982. They are considered as low-grade tumours (WHO grade II), with an 89% 5-year survival.2 They are usually arising from the lateral ventricle, rarely the third ventricle. It usually affects young adults in their 30s (average age is 30 years).1 Although they are considered essentially benign in many cases, there are some reported cases of atypical neurocytomas with a higher proliferation rate.4

CNs are described having an origin from grey matter nuclei in the septum pellucidum. This thought resembles the hypothesis given by Hassoun et al 4 that the possibility of having CNs outside the lateral or third ventricular system is almost nil. So, it is exceptionally rare to have CNs in the fourth ventricle or cerebellum.

Surgical excision has been considered as best in the management of these tumours. Reduction in proliferation rate following radiotherapy has been reported in some studies.5 For this reason, postoperative radiation can be considered in cases with incomplete resection of tumours or in tumours with higher proliferation rate.2

Our case was unique because of two reasons. One, it was a CN of the fourth ventricle; two, our patient was a child of 8 years, as CNs are uncommon in the paediatric age group. So, CNs should be considered in the differential diagnosis of fourth ventricle mass even in the paediatric age group although they are extremely rare. IHC is essential to differentiate CNs from other tumours like oligodendrogliomas and ependymomas. Surgical excision is the primary modality of treatment. A systemic review of the literature has been done and described in table 1.

Table 1

Review of literature

Learning points

  • Central neurocytoma should be considered in the differential diagnosis of posterior fossa tumours even in the paediatric age group.

  • Immunohistochemistry plays an important role in differentiating from other similar looking tumours on microscope like ependymoma and oligodendroglia.

  • Surgical excision is the primary modality of treatment for central neurocytoma.

References

Footnotes

  • Contributors PR prepared the manuscript. RN designed and drafted the work. DA collected and analysed the data. GM approved the final version of the work.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Patient consent for publication Parental/guardian consent obtained.

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