Presentation
Scalp lump.
Patient Data
A sizable extra-axial mass with central calcification extends through the bone and elevates the scalp.
There is a large extra-axial right occipitoparietal convexity T1 and T2 isointense solidly enhancing tumor. There is trans osseous invasion of the overlying right paramedian parietal bone with extracranial subgaleal tumor extension. There is a focal area of flair hyperintensity in the parietal white matter anterior and inferior to the lesion. The lesion is very close to the right lateral wall of the posterior third of the superior sagittal sinus with focal invasion of the right side of the sinus; the sinus is narrowed but not definitely occluded. MR venogram was not performed on this occasion. Within the central aspect of the lesion there are punctate areas of susceptibility corresponding to the calcification noted on the CT scan.
There is no other intracranial mass lesions. There is no signal alteration in the brain parenchyma.
IMPRESSION:
There is extra-axial right parieto-occipital convexity solidly enhancing tumor with transosseous invasion; the imaging appearances are most probably of a meningioma. Hemangiopericytoma can also be considered but the presence of calcification is atypical, and generally haemangiopericyytomas destroy bone rather than 'pass through it'.
Case Discussion
Patient went on to have a resection.
Histology
MICROSCOPIC DESCRIPTION:
The sections show a moderately cellular meningioma with infiltration into the attached dura. Several nests are in vascular spaces in the dura. The tumor forms whorls. No sheeting arrangement is seen. The tumor cells have enlarged ovoid nuclei with prominent nucleoli. There are up to 12 mitoses per 10 high power fields. Scattered small areas of necrosis are noted. A small amount of cerebral cortex is present and no brain invasion is identified. There is no evidence of malignant change. The features are those of an atypical meningioma. The Ki-67 index is about 18%. Most of the tumor cells are progesterone receptor negative.
Sections of the bone show full thickness invasion by meningioma.
DIAGNOSIS:
Atypical meningioma (WHO Grade II)
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