硬膜外に著明な進展を認めた孤立性形質細胞腫の1例

A Case of a Solitary Plasmacytoma Extending into the Extradural Space

Ⅰ．はじめに

　形質細胞腫は形質細胞がモノクローナルに増殖する腫瘍で，ほとんどは多発性骨髄腫として生じるが，稀に孤立性のものがみられる．孤立性の場合も大部分は骨髄内から発生する髄内性だが，骨髄外から発生する髄外性の場合は咽頭や扁桃腺，副鼻腔などから発生する腫瘍が多く，硬膜からの発生は報告が少ない^2,11)．今回われわれは，硬膜から発生し硬膜外に進展する孤立性形質細胞腫の1例を経験したので報告する．

　Plasmacytomas are characterized by a monoclonal proliferation of plasma cells, and constitute the bulk of multiple myeloma. A solitary plasmacytoma is a rare entity, and is even more unlikely to occur intracranially. Here we present a 62-year-old man with an intracranial tumor. Magnetic resonance imaging revealed a large mass on the surface of the right fronto-parieto-temporal region, with extradurally directed growth. The tumor was enhanced homogenously by gadolinium, with dural tail-like findings, which resembled a meningioma. Head computed tomography scan showed osteolytic changes of the calvarium. Tumor removal following intravascular embolization was performed. The tumor seemed to have developed from the dura mater because it was firmly adhered to the dura but not to the calvarium. Histopathological analysis revealed monoclonal proliferation of plasma cells, which were positive for CD56, CD138, and lambda chain, on immunostaining. Since a systemic examination showed no evidence of other lesions, we diagnosed the tumor as a solitary dural plasmacytoma. There was no recurrence after postoperative radiotherapy. Rare entities, such as a solitary plasmacytoma, should be considered when an intracranial lesion with atypical radiological features is observed. If the lesion is anatomically resectable, histopathological evaluation is essential.