Anaplastic meningioma with abundant extracranial metastases: a case report

BACKGROUND: Most meningiomas are classified as WHO CNS grade 1 and have a favorable prognosis when completely resected. In contrast, intracranial recurrence and metastasis are frequently observed in grade 2-3 meningiomas, although extracranial spread is rare. CASE PRESENTATION: A 59-year-old Japanese male presented with numbness on the right side of face and diplopia, and imaging revealed a lesion extending from the right middle cranial fossa to the paranasal sinuses and right optic canal. Histology revealed epithelioid nests and spindle cells with high cellularity. The epithelioid component formed whorl-like structures resembling meningothelial cells, with focal necrosis, bizarre nuclei and lower mitotic activity, which is consistent with atypical meningioma of the meningothelial subtype. In contrast, the spindle cell component demonstrated poor morphological differentiation and high mitotic activity. Immunohistochemistry revealed that the meningothelial cells were positive for epithelial membrane antigen and were partially positive for progesterone receptor. The spindle cells were negative for these markers and weakly positive for smooth muscle actin. The final diagnosis was anaplastic meningioma (WHO CNS grade 3) with sarcomatous features showing smooth muscle differentiation. Extensive extracranial metastases via the sarcomatous element involved 12 extracranial organs, including common sites such as the lungs, bones, and liver, indicating unusually widespread dissemination. CONCLUSION: This report describes an anaplastic meningioma with multiple extracranial metastases. The extensive multiorgan involvement and rapid progression by the autopsy confirmation distinguish this as a rare case with markedly greater malignancy than typically reported.