MNG-07 A CASE OF TRANSFORMED ANAPLASTIC MENINGIOMA IN 18 YEARS

INTRODUCTION: Although 95% of meningiomas are benign tumor (WHO grade I), they rarely exist malignant transformation. It is well known that WHO II or III meningiomas rapidly grow and recurrent frequently. However, there are no common sense about duration of malignant transformation between previous reports. Here we report a case of anaplastic meningioma which showed malignant transformation in 18 years. CASE: The patient was 77-year-old man. He was pointed out as having a 20-mm mass in the left occipital convexity at brain checkup 19 years before. After 6 months, the mass was totally removed (Simpson grade I) at previous hospital. Histopathological diagnosis revealed meningioma with psammoma body, whose Ki-67 index was below 1 %. Postoperative course was good and periodic follow up was abandoned. The patient presented with consciousness disturbance and right hemiparesis after 18 years from the first operation. CT scan showed a 30-mm mass with intratumoral hemorrhage and perifocal edema in the left occipital lesion. Tumor removal was performed. The border of the tumor was clear and the macroscopic view was compatible with meningioma at intraoperative findings. The tumor was removed as much as possible, but partially remained which were extended to superior sagittal sinus (Simpson grade III). Histopathological findings were anaplastic meningioma with sarcoid change, whose Ki-67 index was 70%. His neurological abnormality improved postoperatively. DISCUSSION: In the previous report, anaplastic meningioma is a rare tumor, which is 1% of whole meningioma. The rate of malignant transformation is reported 12–38%. The cause of malignant transformation is reported to be radiation therapy, mechanical stimulation by surgical manipulation, viral infection, and loss of chromosome. Although recurrence rate is low at total resection of meningioma, there rarely exists malignant transformation after a long period of time like our case.