Schwannoma - foramen magnum

Case contributed by Frank Gaillard
Diagnosis certain

Presentation

Weakness.

Patient Data

Age: 40 years
Gender: Male
ct

A rounded lesion slightly hypodense compared to the brain, displaces the cervicomedullary junction to the left. 

mri

A sizable near-spherical extra-axial tumor at the level of foramen magnum arising from the lateral aspect of C0/C1 at the site where the left vertebral artery pierces the dura compresses the medulla posterolaterally towards the right without cord signal abnormality. A 7 mm extradural component is seen immediately below the vertebral artery continuity with the larger intradural component. The mass has high T2 signal, with heterogeneous areas of signal loss, avidly enhances, and is very well circumscribed. The left vertebral artery is compressed between the mass and the left occipital condyle but continues to have flow-signal within it. The remainder of the brain is unremarkable. No hydrocephalus. No other lesions.

Conclusion: Dumbbell shaped mass (large intradural, small extradural component) most likely represents a schwannoma of the C1 nerve root on the left, rather than a meningioma which is the alternative diagnosis.

Case Discussion

The patient went on to have a resection. 

Histology

The tumor has spindle cells with wavy nuclei and tapering eosinophilic cytoplasm. No significant nuclear pleomorphism or malignant features are seen. Immunohistochemistry shows tumor cells stain strongly positive with S100 and negative with FSTR2.

DIAGNOSIS: Schwannoma.

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