Presentation
Recent right-sided paresthesia.
Patient Data
The frontal horn of the left lateral ventricle is expanded by a very high T2 signal mass, which partially attenuates on FLAIR and demonstrates a low T1 signal and no solid enhancement. The mass has fairly low DWI signal, lower than normal white matter and very facilitated diffusion on ADC. Spectroscopy demonstrates minor elevation of choline and no elevation of CBV. No calcification or blood product.
A small vessel courses through the mass from the ependymal surface. A rim of high T2 signal is present adjacent to the mass. it is an isolated abnormality.
Conclusion:
This is an unusual mass. The age and size make a subependymoma less likey. An ependymoma, when supratentorial, tends to be parenchymal rather than intraventricular, and enhancement is usually present. A central neurocytoma usually enhances somewhat and arises form the setptum pellucidum. A myxoid glioneuronal tumor would have these signal characteristics but it is a rare entity.
Case Discussion
The patient went on to have a resection.
Histology
Sections show fragments of a tumor comprising small round to oval nuclei with finely vesicular chromatin and inconspicuous nucleoli, set amongst a markedly myxoid and focally fibrillary background with scattered capillary-sized blood vessels. Tumor cells are mostly dispersed, with focal clustering and some perivascular rosette-like arrangements. No mitoses, necrosis or microvascular proliferation was seen. A couple of fragments, including ventricle wall tissue with attached tumor. There is no convincing neuronal component identified on synaptophysin and CD34 immunohistochemistry.
Immunohistochemistry
GFAP - Positive
OLIG2 - Positive
IDH-1 R132H - Negative (not mutated)
ATRX - Intact (not mutated)
p53 - wild-type pattern (not mutated)
MTAP- Intact (CDKN2A not deleted)
SOX10 - Positive
Ki67 index - <5%
Final diagnosis
Myxoid glioneuronal tumor, CNS WHO grade 1
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