Meningioma - volcano sign
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There is a large extra-axial solid tumor within the left frontotemporal region compressing the adjacent brain parenchyma, which shows a small rim of edema and causing an 8 mm rightward midline shift and mild left uncal herniation. It has a heterogeneous signal intensity that is predominantly low on both T1 and T2 weighted images, showing vivid and intense contrast enhancement. The lesion is durally broad-based with signs of associated bone hyperostosis.
A posterosuperior lobulated extra-axial tumor, although showing a different signal pattern and less vivid enhancement, is felt part of the same process.
There is a 10mm right postcentral gyrus cavernous malformations is noted.
Conclusion: features are those of two, probably connected, left-sided meningiomas.
Although radiology probably has enough named signs, I think this appearance warrants a new one. The volcano sign! It represents the triangular hyperostosis often seen at the site of initial growth of a meningioma, which coincides with the intratumoral vascularity (sunburst sign or spoke wheel sign).
When viewed side on, the hyperostosis and tumoral flow-voids are reminiscent of an exploding volcano.
The patient went on to have a resection of both masses.
First larger lesion: paraffin sections show a moderately cellular dural-based tumor. This is composed of spindle cells arranged intersecting fasciculi within a dense hyalinised fibrous stroma. Tumor cells show mild nuclear pleomorphism. No mitotic figures or areas of necrosis are seen. There is no evidence of brain invasion.
Second smaller lesion: paraffin sections show a moderately cellular meningioma. This has well-developed syncytial architecture. Tumor cells have uniform nuclear features. No mitotic figures or areas of necrosis are identified.
Immunohistochemistry results show tumor cells stain EMA+, PgR-, SSTR2a+ and STAT6-.
FINAL DIAGNOSIS: meningioma (WHO Grade I).