早期胃癌Ⅱb病変の成り立ちに関する病理組織学的研究

Histopathological Study on Ⅱb Lesions of the Gastric Carcinoma with Reference to the Mechanism of Their Development

　Ⅱb型早期胃癌（以下Ⅱbとする）は，周辺正常粘膜と高低の差がないために，X線・内視鏡診断学が進歩した今日でもその診断は極めて困難であり，われわれが日常Ⅱbに接する機会は多くはない．Ⅱbと診断される症例のうちで最も多いのは5mm以下の微小癌であり，その大部分は切除胃の組織学的検索によって発見されたものである．6mm以上のⅡbが少ない理由として，胃癌はその発生より極めて短期間の時点においては，大部分がⅡbの形態をとり，癌発育・進展の過程で正常粘膜に比べてびらん・潰瘍化しやすい傾向のある癌では陥凹や潰瘍が形成され，一方，びらんや潰瘍による癌の部分的脱落の傾向が弱い癌では隆起性発育を示す．そして，極めて少数の胃癌は正常粘膜と高低差のないままの状態で発育・進展し，Ⅱbとして認識される形態を呈すると考えられる．このように，診断が困難であるⅡbの形態はどのような環境において成立するかが問題となる．なぜならば，もしその環境が解明されるならば，胃癌の診断に際して，その環境を考慮することによってⅡb診断の向上をはかることができると考えられるからである．

　本研究は，Ⅱbの存在する胃の背景粘膜，特にⅡbの周辺部の非癌粘膜について病理組織学的に検討し，Ⅱb成立の宿主粘膜要因について考察を試みた．

　Type of Ⅱb of the early carcinoma of the stomach has been defined as carcinoma almost non-recognizing elevation or depression from the surrounding mucosa at the level, and it is very difficult to diagnose it preoperatively. Although a considerable number of these reports have appeared in recent years, little is known about the mechanism of development of Ⅱb lesions including type Ⅱb per se and partial Ⅱb lesion accompanied with other types of carcinoma. The purpose of this paper is to study histologically the Ⅱb lesions of the gastric carcinoma with reference to the mechanism of their development.

　Subjects for this study consisted of nine cases of type Ⅱb per se, and 30 cases of carcinoma partially accompanying with Ⅱb lesions. As the controls, 31 cases of type Ⅱc (depressed type) were used. These resected stomachs were histologically examined by serially cutting method as shown in Figs. 1b, 2b, and 3b. Gastric mucosa neighboring the Ⅱb lesions was divided according to severity of intestinal metaplasia and mucosal atrophy into three grades, as shown in Table 2.

　In general, gastric mucosae harboring the Ⅱb lesions showed atrophy, especially markedly in the antrum and corpus through the lesser curvature site. There was a tendency that the neighboring mucosae of the Ⅱb lesions showed histologically marked atrophy and intestinal metaplasia, independently of histological types of carcinomas (Tables 4 and 6). These findings in the neighboring mucosae were usually more remarkable than that of the controls.

　In the 30 carcinomas partially accompanying with the Ⅱb lesion, localization of the partial Ⅱb lesion were studied. In 16 carcinomas located in the area through the lesser curvature, the partial Ⅱb lesions were distributed evenly around them. Whereas, in 14 carcinomas located in the anterior and posterior walls, the partial Ⅱb lesions existed at the lesser curvature side of the carcinomas.

　There is the tendency that the carcinoma extending the mucosa is more easily eroded or ulcerated by peptic mechanism than the non-affected mucosa. Therefore, taking the tendency into consideration, those results suggest that carcinoma develops as the Ⅱb lesions when it spreads into markedly atrophic mucosa.