成人大脳半球に生じたpilocytic astrocytomaの1例

A Case of Pilocytic Astrocytoma in an Adult

Ⅰ．はじめに

　毛様細胞性星細胞腫（pilocytic astrocytoma：PA）は，星細胞性腫瘍の1つであるが，通常型といわれるびまん性星細胞腫とは異なり，限局型に分類される特殊な星細胞腫である²⁰⁾．WHO分類ではGrade 1に分類される生物学的悪性度の低い腫瘍である．主に小児，若年者に発生し，成人発生例は稀といわれている⁸⁾．今回われわれは右頭頂葉に発生した囊胞性のPAの1例を経験したので報告する．

　Pilocytic astrocytoma is the most common glioma in children, in whom the majority arise in the cerebellum. In contrast, pilocytic astrocytomas are less common in adults. The most frequent locations involved are the basal ganglia, cerebellum, optic chiasm, and hypothalamus. Overall survival rates are good. The case presented involved a pilocytic astrocytoma of the right parietal lobe in a 36-year-old man. Cranial magnetic resonance imaging (MRI) revealed a small mural nodule in the wall of the cyst, with no edema around the tumor. This nodule showed a hyperintense signal on gadolinium-enhanced MRI. Computed tomography (CT) scanning revealed a hypodense right parietal lobe mass with calcification. At surgery, the cyst contents were aspirated, and the mural nodule was excised. Postoperative radiotherapy was not given. Neuropathological examination revealed a pilocytic astrocytoma (Grade I). The MIB-index was 3.3%. There has been no recurrence after 1 year of postoperative follow-up.