Anaplastic astroblastomaの鑑別診断と治療--症例報告と文献的考察

Differential Diagnosis of and Therapy for Anaplastic Astroblastoma: Case Report and Review of the Literature

Ⅰ．はじめに

　Astroblastomaは稀な原発性脳腫瘍の1つであり，glioma全体の約0.45～2.8%と推定されている^12,30)．1930年にBaileyとBucyが25例のシリーズを初めて報告し，1989年にBonninとRubinsteinがその病理所見からlow grade/well-differentiatedとhigh grade/malignant（anaplastic）に分類し，予後が異なることを報告した^2,5)．しかし最新のWHO 2007年版の脳腫瘍分類では，astrocytoma，oligodendroglioma，ependymomaとは異なるother neuroepithelial tumorとして分類されているものの，その予後や治療については未だ議論のある点もありWHO gradeは定められていない²⁰⁾．今回，われわれは著明な血管増生を認めたanaplastic astroblastomaの1成人例を経験したので，その診断と治療について文献的考察を加え報告する．

　Astroblastomas are rare glial tumors. We report a case of 33-year-old woman with high-grade astroblastoma with hypervascularity. She had a one-month history of right visual disturbance and papillar edema. MRI revealed a lobulated mass with cysts and flow voids in the right superficial frontal lobe, a phenomenon described as “bubbly appearance”. Right carotid angiography demonstrated marked tumor stain and early venous filling. MR spectroscopy showed an increase in myoinositol and the choline/creatine ratio, and decreased N-acetyl aspartate. The lipid and lactate level was not increased. The well-circumscribed tumor was totally resected. Histological examination showed perivascular pseudorosettes and hyalinization of blood vessels with high cellularity, anaplastic nuclear features, focal necrosis, mitosis, and endothelial proliferation. Immunohistochemically, glial fibrillary acidic protein and S-100 protein were intensely positive and the MIB-1 labeling index was high（20%）in the tumor cells. Based on these findings, a diagnosis of high-grade astroblastoma was made. The patient received postoperative radiotherapy and chemotherapy with temozolomide and suffered no relapse in the course of 3 years after surgery. Characteristically, astroblastomas manifest a “bubbly appearance” and a lobulated mass on MRI scans. As these tumors tend to be hypervascular, angiograms are useful for designing the operative strategy. However, their low-or high grade is difficult to ascertain preoperatively based on MRI-, MRS-, and DSA findings. The standard therapy for high-grade astroblastoma is total resection and postoperative radiation therapy. As the incidence of tumor recurrence is high, we recommend additional chemotherapy with TMZ.