円蓋部髄膜腫全摘出後26年で悪性髄膜腫として再発した症例

A Case of Recurrent Convexity Meningioma with Malignant Transformation 26 Years After Total Tumor Removal

I．はじめに

　われわれは，九州大学で1966年から1992年の間に手術を行った570例の髄膜腫患者の中で，下記の条件，1）初回腫瘍全摘術，2）術後頻回の経時的画像評価，3）過去にBrdUでの増殖能評価，これらの3条件を満たす患者33人を1）非再発群，2）再発群，3）転移群の3つのグループに分け，臨床経過とMIBI（Ki−67）staining index（MIB1 SI），BrdU labeling index，組織学的悪性度との相関を調べた．その結果，MIB1 SIと組織学的悪性度は臨床経過と良く相関し有意差を認めたので術後治療方針を立てる上で良い指標となり得ると1994年に報告した^8）．一般に，髄膜腫は組織学的悪性度に応じて，再発あるいは再増大までの期間が短くなる傾向がある^3），4）．今回，円蓋部髄膜腫全摘後約26年で再発を認め，再発後約2年半の問に急速に増大した症例を経験した．病理組織評価で初発時は異型度が低かったのに対し，再発時には悪性度がきわめて高く，MIBI SI^7）も高値を示したので報告する．

Meningiomas are common intracranial tumors, the majority of which are considered benign. However, they sometimes show altered biologic behavior, associated with local aggressiveness and late distant metas- tasis. We report a patient with a convexity meningioma, which recurred as a malignant transformation 26 years after a total tumor removal. A 75-year-old man was transferred to a local hospital because of general convulsions and left hemiparesis. The patient had had an operation for the total removal of a right frontal convexity meningioma at the age of 46 and had been free of its effects until the age of 72.Brainmagneticresonance imaging (MRI) showed a recurrent tumor located in the anterior area of the previous cra-niotomy. Over the following two and a half years, MRI revealed rapid enlargement and infiltration of thetumor into the brain parenchyma. The primary tumor was nodular, macroscopically well demarcated fromthe surrounding brain tissue and, histologically, was a transitional type of meningioma without any atypic-al features. In contrast, the recurrent tumor, whose border was ill-defined, had invaded the neighboringbrain. A histological specimen of the recurrent tumor showed highly malignant features such as necrosis,intracerebral infiltration, dense cellularity, and high proliferating activity as demonstrated by a cell kineticstudy using the MIB 1 staining index. We should be mindful that recurrence from common benign typemeningiomas may occur as malignant transformations after more than two decades.