Atypical meningioma - grade 2

Case contributed by Assoc Prof Frank Gaillard

Presentation

Lump near vertex.

Patient Data

Age: 55 years
Gender: Male
MRI

There is a large extra-axial parafalcine heterogeneously enhancing mass at the parietal vertex. The mass is hypointense on the T2-weighted sequence, and shows restricted diffusion with ADC values similar to normal brain.  There is clear invasion into the superior sagittal sinus, for about 55 mm in length.  The parietal portion of the superior sagittal sinus is occluded. The tumor invades through the parietal skull at the vertex, more so on the right side.  The aponeurosis is elevated and thickened, without definite tumor invasion across the aponeurosis.

There is no definite invasion into the brain parenchyma.  No significant vasogenic edema.

The remainder of the brain and the calvarium is unremarkable without additional lesion is detected.

Conclusion:

Large parietal parafalcine tumor with invasion into the superior sagittal sinus and the parietal skull.  Although this may represent a meningioma, differentials such as solitary fibrous tumor would also require consideration given the imaging appearance.  The other possibilities would include metastases and myeloma.

Case Discussion

The patient went on to have a resection. 

Histology

Sections show a meningeal base tumor which is attached to the dura.  The tumor consists of ahypercellular tumor which has sheet-like growth pattern with large nodules separated by fibrous bands.  Thetumour cells have oval nuclei with small nucleoli.  No significant nuclear pleomorphism is seen.  The cellshave a small amount of eosinophilic cytoplasm.  The tumor has increased cellularity with areas of sheet-likegrowth pattern.  Areas with small cell-like change are present.  Mitotic figures are not conspicuous up to 2 mitoses per 10 high power field are seen.  Immunohistochemistry shows tumor stains strongly positive with SSTR2 and negative for STAT6. 

 Bone flap:  Decalcified sections show bone with focal fibroblastic tissue. No tumor identified

Final diagnosis:

Atypical meningioma WHO grade 2

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