Presentation
Headache.
Patient Data
A heterogeneously enhancing extra-axial solid mass with a large cystic component is noted on the left. Underlying sulci and gray matter are distorted. Some underlying vasogenic edema significant mass effect are present.
The solid component demonstrates some restricted diffusion (similar ADC to parenchyma). Punctate susceptibility on the gradient echo sequences with no identifiable calcification on the CT (not shown) likely represents hemosiderin.
Conclusion: The imaging characteristics are somewhat atypical, while the large cystic component and the lack of significant contrast enhancement on CT is atypical for meningiomas, however the extraaxial location, diffusion restriction and the overall high prevalence of meningiomas suggests that meningioma is most likely, particularly an atypical or malignant meningioma. Other differentials include meningosarcoma or hemangiopericytoma.
The patient went on to have surgery.
Histology
MACROSCOPIC DESCRIPTION: A sheet of roughly triangular cream tissue consistent with dura, 65x50mm in cross section. One of the surfaces is smooth. The opposite surface is focally ragged and few small cream papillary outgrowths are seen.
MICROSCOPIC DESCRIPTION: The sections show a moderately cellular tumor with infiltration into the attached dura. It comprises whorls and fascicles. In some areas, there is a loss of whorls with sheeting arrangement. Microcystic change is present in the background. The tumor cells have ovoid nuclei and prominent nucleoli. There is no small cell change. Up to 5 mitoses per 10 high power fields are seen. There are occasional foci of necrosis. No brain parenchyma is included in the biopsy. The dura is chronic inflamed. The features are those of atypical meningioma. There is no evidence of malignant change. Less than 5% of the tumor is progesterone receptor positive. The Ki-67 index is about 8%.
FINAL DIAGNOSIS: Atypical meningioma (WHO Grade II).
Selected multiplanar images demonstrate multiple extra-axial solid enhancing tumors scattered along the left cerebral hemisphere: left anterior frontal, left posterior frontal parafalcine, left frontoparietal region at the vertex, and left posterior temporal region. These have been increasing in size over the last years.
The patient underwent a new resection due to the recurrent tumor.
MICROSCOPIC FINDINGS: The sections show a meningioma with attached dura. There is mild increase in cellularity. The tumor forms sheets. Whorls are inconspicuous. The tumor cells have focal mildly enlarged nuclei with conspicuous nucleoli. There are up to 5 mitoses per 10 high power fields. No necrosis is seen. No brain parenchyma is present. There is no evidence of malignant change. The dural edges appear clear of tumor. The features are those of atypical meningioma. The Ki-67 index is about 10%. About 5% of the tumor cells are progesterone receptor positive.
DIAGNOSIS: Left parietal lesion: Atypical meningioma (WHO Grade II).
Case Discussion
Atypical meningioma (WHO Grade II) is a more aggressive subtype of meningioma that has significantly higher five-year recurrence rate (41%) compared to that seen in grade I (benign) meningiomas (12%).
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