Presentation
Four week history of occipital headache.
Patient Data
Multiple enhancing extra-axial lesions of the posterior cranial fossa. Largest lesion is centered at the anterior aspect of the right cerebellar hemisphere. Homogenous hypointense appearance on T1 and mild hyperintense appearance on T2/FLAIR relative to the grey matter. Hyperintense on diffusion-weighted imaging with corresponding low ADC values (500-600 x 10-6 mm2/s. Absence of flow void associated with the lesions. No susceptibility artifact suggestive of calcification and hemorrhage. No evidence of bony involvement.
There is surrounding vasogenic edema causing mild mass effect with leftward displacement of the middle cerebellar peduncle and partial effacement of the fourth ventricle. Cerebellar tonsils are positioned 13mm below the foramen magnum. Obstructive hydrocephalus with subependymal edema demonstrated by the presence of periventricular white matter T2 FLAIR hyperintensity.
Conclusion: Multiple solid enhancing extra-axial lesions of the posterior cranial fossa with differentials including atypical appearance of meningiomata and lymphoma.
Case Discussion
The patient underwent stereotactic retrosigmoid craniotomy and gross total resection of the largest cerebellar lesion.
Histology
Sections show cerebellum infiltrated by a highly cellular tumor. The tumor forms sheets. The tumor cells have oval-to-elongated nuclei, coarse chromatin, inconspicuous nucleoli, and small amounts of eosinophilic cytoplasm. Mitotic figures are extensive as are apoptotic figures. Vague Homer Wright rosettes are seen. Thin-walled blood vessels traverse the tumor. There are no desmoplastic/nodular components. There is no frank anaplasia.
- Positive
- Synaptophysin
- Negative
- p53
- GAB1
- YAP1
- IHD1
- R132H
- p16
- Chromogranin
- NeuN
- CD45
- Ki67 index 50%
FINAL DIAGNOSIS: Classic medulloblastoma non-WTN/non-SHH (WHO grade IV)
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