チロシン水酸化酵素陽性神経細胞の出現を認めた頭頂葉ganglioglioma

THE OCCURRENCE OF TYROSINE HYDROXYLASE-IMMUNOREACTIVE NEURONS IN A PARIETAL LOBE GANGLIOGLIOMA

　抄録　頭頂葉gangliogliomaの1生検例（61歳，男性）において，カテコラミン生合成の律速酵素であるチロシン水酸化酵素（TH）に対する抗体を用い免疫組織化学的検索を行なった。腫瘍は，光顕的に多数の神経細胞と腫瘍性アストロサイトの増生より成り，電顕的には多数のdense core vesicle （DCV）が神経細胞の胞体や神経突起内に認められた。TH免疫組織化学では，少数ながら陽性神経細胞の出現が認められ，その胞体は種々の形態を示し，ときに二核や多核を呈していた。従来gangliogliomaは特徴的なDCVの存在などから一般に末梢自律神経系由来の過誤腫であると考えられてきたように思われる。しかし最近，ヒト正常大脳皮質においてもTH陽性神経細胞の存在が明らかとなった。このことを考慮すると，大脳において正常に形成されるべきTH陽性神経細胞がその発生・分化の段階で迷入または混入してできるようなanomalousあるいはdysgenetic focusをgangliogliomaの発生母地として想定することも可能と考えられた。

A parietal lobe ganglioglioma in a 61-year-oldmale was investigated ultrastructurally and immu-nohistochemically, using antiserum against tyrosine hydroxylase (TH), a rate-limiting enzyme of the catecholamine (CA)-synthesizing pathway.

On light microscopy, the tumor was composed mainly of neuronal and astrocytic cells. The neu-ronal cells had typical round vesicular nuclei with prominent nucleoli and showed abundant cyto-plasm with variable amounts of Nissl bodies. Bi-nucleated neuronal cells were occasionally found. The astrocytic cells had eosinophilic cytoplasm of variable shapes and hyperchromatic small nuclei. Electron microscopy revealed numerous dense core vesicles (DCVs) in the neuronal cytoplasm and pro-cesses.

Immunohistochemically, TH-immunoreactive neu-ronal cells were found sporadically in the tumor tissue. They were often binucleated or multinucle-ated.

The presence of TH-immunoreactive neuronal cells in the present case is of interest in consider-ing the origin of neuronal cells in ganglioglioma. Some investigators have considered that they may arise from the ectopic autonomic neuronal cell nests in view of the presence of DCVs. However, Gasper et al. have recently demonstrated the pre-sence of TH-immunoreactive neurons in the normal human cerebral cortex. Therefore, it may also be possible to consider that TH-immunoreactive neu-ronal cells in this tumor originated from a certain dysgenetic focus containing such TH-immunoreac-tive neurons in the developmental stage.