術中所見が髄膜腫と類似した頚静脈結節部primary dural lymphomaの1例

A Case of Primary Dural Lymphoma of Jugular Tubercle Mimicking Lower Clival Meningioma

Ⅰ．はじめに

　Primary dural lymphoma（PDL）は稀なprimary central nervous system lymphoma（PCNSL）の1種で，病理学的には硬膜由来のextranodal marginal zone lymphoma of mucosa-associated lymphoid tissue type（MALTリンパ腫）であることが多い．その疫学的特徴や画像所見は髄膜腫に酷似しているため鑑別が困難である^1,6,8)．われわれは，片麻痺と眼球運動障害を主訴に入院し画像検査で頚静脈結節部の髄膜腫と診断されていたが，術後の病理診断でPDLと診断された症例を経験した．PDLに関する過去の報告を渉猟し，その臨床像と治療予後について文献的考察を行った．

　Primary dural lymphoma（PDL）is a rare type of primary central nervous system lymphoma（PCNSL）;however, its clinical etiology and appearance on magnetic resonance images（MRI）are similar to those of meningioma. We report a case of PDL mimicking a meningioma in the jugular tubercle, with hemiparesis and double vision, and review the published PDL case reports.

　A 41-year-old woman experienced numbness on her right side, and reported right hemiparesis and double vision 2 days thereafter. Her cranial computed tomography（CT）scan showed a mass lesion in the posterior fossa, and contrasted MRI revealed homogenous tumor with a dural tail sign in the left jugular tubercle. The patient was diagnosed as having jugular tubercle meningioma. However, her symptoms disappeared promptly with the injection of dexamethasone, and follow-up MRI showed that the tumor had diminished. After 9 months, her double vision recurred and MRI results indicated tumor regrowth. She underwent sub-total resection of the tumor via the left trans-condylar fossa approach. A histological diagnosis was PDL. She was treated with 3 courses of high-dose methotrexate, and subsequent MRI results showed a partial reduction of the residual tumor.

　PDL is histologically associated with marginal zone lymphoma（MZL), and is sensitive to radiation and chemotherapy. This patient responded well to high-dose methotrexate alone. PDL is one of the important differential diagnoses of meningioma.