Presentation
Initial presenting complaint was headache. CT at the outside hospital revealed a large cerebellar mass.
Patient Data
The cerebellum is enlarged with a mass displaying abnormal signal intensity center along the cerebellar vermis with predominant involvement of the left cerebellum. The lesion is associated with mass effect most pronounced on the dorsal pons and tectum with near-total obliteration of cerebral aqueduct. There is effacement of the fourth ventricle. The mass is predominantly T2 hyperintense with alternate high and normal signal intensity areas. There is a striated appearance with hypointense and isointense bands on T1 best appreciated on sagittal postcontrast images. There is no definite solid or nodular enhancement seen.
Case Discussion
This a case of a large cerebellar neurocytoma. The patient underwent a suboccipital craniotomy with cerebellar debulking and C1 laminectomy. Histopathologic revealed cerebellar tissue with foci of neurocytoma. Immunohistochemistry showed that the tumor was positive for Neu-N and Synaptophysin, with a low proliferative activity (Ki-67: <1%; low PHH3) and low P53 (<1%).
Central neurocytomas are rare WHO grade 2 primary central nervous system tumors that primarily occur within the lateral ventricle and have an incidence rate of 0.022 per 100,000.1 As the name implies, extraventricular neurocytomas are neurocytomas that occur outside of the ventricular system. These are far less common with an incidence rate of 0.009 per 100,000.1 In even rarer cases, such as this case, extraventricular neurocytomas may develop within the cerebellum. An analysis of 201 patients with extraventricular neurocytomas showed that only 13 patients (6.5%) developed the neurocytoma within their cerebellum.2
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