Extracranially extended meningothelial meningiomas with a high MIB-1 index: a report of two cases.

Meningiomas that extend from the meninges to the extracranial tissue and result in skull osteolysis have been known to take an aggressive clinical course. Two such cases in elderly patients are reported. Case 1 is an 82-year-old woman who had undergone removal of the parasagittal meningioma (meningothelial meningioma with 5% of MIB-1 index) 4 years and 6 months previously, developed recurrence of the tumor that extended to extracranial soft tissue. Biopsy obtained from the subcutaneous tissue showed an atypical meningothelial meningioma with 20% of MIB-1 index. In case 2 an 84-year-old man, who developed rapidly progressing dementia and gait disturbance, the MRI study revealed an intracranial-extraaxial right frontal tumor with an extracranial extension resulting in skull osteolysis. Pathological examination of the totally resected tumor identified meningothelial meningioma, but MIB-1 index of the intracranial portion of the tumor was less than 0.1%, while that of the extracranial portion was approximately 15%. Although the meningiomas presently reported failed to show histological features of malignancy, the high MIB-1 index indicated that they were rapidly growing tumors. In the present report it is considered that meningioma cells that invade the skull and extracranial tissue are biologically aggressive and require total resection, as long as the condition of the patients is feasible for surgery.