PMC8769411_01
MRI. (A) Axial T1-weighted MRI shows a well-circumscribed hyperintense lesion in the foramen magnum. (B) Axial T2-weighted MRI reveals hypointensity. (C, D) Axial and sagittal gadolinium-enhanced T1-weighted MRI shows an intradural extramedullary mass lesion in the foramen magnum is compressing the dorsal brainstem. The contrast enhancement is not evident. (E) Postoperative axial gadolinium-enhanced T1-weighted MRI show gross total removal. MRI: magnetic resonance imaging.
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F1
The mass was hyperintense on T1-weighted images but without clear contrast enhancement, and hypointense on T2-weighted images (Figs. 1A-1D). A follow-up examination 2 years after surgery, MRI showed no evidence of tumor recurrence (Fig. 1E).
Intraoperative microscopic view. A blackish-grey tumor can be seen (A). After peeling off the arachnoid mater around the tumor, gross total removal was achieved (B).
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F2
After a dural incision, a blackish-grey, well-circumscribed tumor, which was located of the foramen magnum behind the medulla oblongata was found (Fig. 2A). After dissecting from the surrounding tissue, gross total removal was achieved and dural attachment was coagulated (Fig. 2B).
Histopathological and immunohistochemical findings. (A) The tumor is composed of relatively monomorphic spindle cells that formed a fascicled or nested growth pattern. There are variable amounts of pigment deposition consistent with melanin in the cytoplasm (hematoxylin and eosin stain, 400x). (B) HMB-45 (+) staining of tumor cells. (C) S-100 (+) staining of tumor cells. (D) MIB-1/Ki-67 labeling index is low.
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F3
The histopathological findings were consistent with meningeal melanocytoma (Fig. 3).