神経系の細網系腫瘍—1生検例の病理組織学的電顕的観察

A CASE OF RETICULAR TISSUE TUMOR OF THE NERVOUS SYSTEM. HISTOPATHOLOGICAL AND ELECTRON MICROSCOPIC STUDIES

Ｉ．はじめに

　中枢神経系（脳と脳膜）の悪性間葉性腫瘍には①線維肉腫Fibrosarcoma，②悪性髄膜腫Malignant meningio—ma，③悪性黒色腫Malignant melanorna，④細網内皮系腫瘍が知られている。脳に原発する細網内皮系腫瘍は当初は類円形肉腫細胞の示す増殖のパターンによつてPe—rivascular, Perithelial sarcoma, Alveolar sarcoma （Ba—iley^5），　1929）と記載されていたが，この腫瘍型が悪性リンパ腫と同質の脳の細網系腫瘍であるという立場からその後，この腫瘍型は原発性細網肉腫として記載されるようになつた^33）。1948年，Russells Marshall and Smith^28）は中枢神経系の細網系がミクログリア中心とするMa・crophage systemであるという立場にたち，またこの型の腫瘍の構成細胞がミクログリアと同質の炭酸銀鍍銀法による好銀性を示すことに注目し，この型の腫瘍をMicrogliomaと命名し，以後この名称は脳原発の細網系腫瘍と同義的にあるいはHodgkin肉腫とともに細網系腫瘍のサブグループの1組織型として扱われている。私達は最近，神経系の細網系腫瘍に特徴的な組織像を示す生検材料について電顕的観察を行なつたので，この腫瘍の超微構成や腫瘍構成細胞の炭酸銀法によるMetalo—philiaの問題について検討し，考察を行なつた。

Histopathological and electron microscopic obser-vations have been made on a cerebral biopsy sample from a 45-year-old patient with a frontal lobe tumor of reticular tissue origin.

Microscopically, the tumor tissue was composed of two areas of different histological pattern. One area was made up of densely packed masses of small rounded cells. The nuclei had pale nucleoplasm and contained distinct nucleoli. Reticulin fibrils were formed between the individual tumor cells. The other area of the tumor showed the histology of perivascular sarcoma. The vessels were cuffed with neoplastic cells. The intervascular neuronal tissue was also infiltrated by scattered tumor cells mixed with proliferating reactive plump astrocytes. The infiltrating cells appeared argyrophil with Penfield carbonate silver impregnation method for microglia.

In electron microscopy the cell type of the tumor constituents was characterized by relatively large nucleus with prominent nucleolus. The cytoplasmappeared scanty in relation to nuclear volume. It had a considerable electron density due to a mul-titude of free ribosomes, but containing only scattered mitochondria. So-called fiber reticulum was found in the intercellular spaces, being occasionally held by neoplastic cell processes. It was composed of amorphous materials and collagenous fibers with cross-banding. Occasional tumor consitituents had ample amount of cytoplasm which contained numbers of vesicles, vacuoles and membrane-bounded lyso-some-like inclusions with a considerable variety in size, density and internal structure. The ultrastru-ctural features seem to simulate those described in malignant lymphoma or reticulum cell sarcoma arizing in the lymph nodes. In areas where the light microscopy showed the histology of so-called "peri-vascular sarcoma", lymphoma cells were observed accumulating in the perivascular space and scattered in the intervascular nervous parenchyma intermixed with the cells identified as neuronal cells and reac-tive astrocytes. Occasional astrocytic cell nuclei were found including "nuclearbodies". The dark cells which had been hitherto identified as micro-glia in electron microscopy were not shared in the process. It is considered that lymphoma cells infiltrating in the nervous parenchyma might be in part electron microscopic equivalent with the cell showing metalophilia in light microscopy. Histopathological studies were also made using Penfield carbonate silver impregnation method for microglia on the lymph nodes and spleen of two autopsy cases with classical type of malignant lymph-oma. A considerable number of proliferating cells were found showing metalophylia. It would seem that the metallophylia is not specific for neoplastic reticular tissue cells of the nervous system and that it does'nt present sufficient basis for subclassifying reticular tissue tumors of the nervous system apart from the problems of malignant lymphoma in general.