術前画像検査で骨肉腫が疑われたintraosseous meningiomaの1例

A Case of Intraosseous Meningioma Suspected of Osteosarcoma Based on Preoperative Image Examinations

Ⅰ．はじめに

　髄膜腫は原発性脳腫瘍の33.8%を占め¹⁵⁾，多くが硬膜に沿って発生するが，ごく稀に硬膜とは無関係に骨原発に発生し，intraosseous meningioma（IM）として今までに複数の報告がある．原発性硬膜外髄膜腫の68%が頭蓋冠を含んでおり，IMに多いとされる部位は前頭頭頂部および眼窩部とされ³⁾，術前の画像診断では，骨肉腫や線維性異形成，類骨骨腫との鑑別が問題となる．今回，術前画像検査で骨肉腫が疑われた頭蓋骨腫瘍が，病理診断でIMであった症例を経験したため，文献的考察を加え報告する．

　Intraosseous meningioma（IM）is one of the less frequent tumors of the skull, which often cannot be distinguished from other common skull tumors based on preoperative radiological findings. Herein, we describe a case of IM suspected to be an osteosarcoma based on preoperative image examinations.

　A 72-year-old woman experienced an impact to her left parietal area, and a subcutaneous tumor appeared in the same area. It had enlarged gradually over seven months, although she exhibited no obvious symptoms. On preoperative diagnostic imaging, the tumor was mainly found in the skull, extending from the subcutaneous area to the intradural space, and was primarily suspected to be an osteosarcoma. After surgery, the pathological diagnosis was atypical meningioma, and there has been no recurrence for 1 year after the surgery.

　It is necessary for IM to be considered as a differential diagnosis for skull tumors exhibiting characteristics of osteosarcoma.