Ⅱb型早期胃癌の内視鏡診断

Endoscopic Diagnosis of Type Ⅱb Early Gastric Cancer

　近年Ⅱb型早期胃癌の報告例が増加してきたがまだそのX線，内視鏡とも確たる診断基準が示されてはいない．

　Ⅱbを探し出そうという努力は，単に診断限界をのばすという興味だけではなく，胃癌の初期像の検討，胃癌の発育の研究のみならず切除範囲の決定というpraktischの要求に対しても答えることができる．

　しかし，まず困ることはⅡbといっても人によりその肉眼的判定には少なからず解釈の相違がみられることである．

　1962年の内視鏡学会分類によるⅡbの定義を振り返ってみるに，肉眼的にみて表面平坦で胃癌の初期像を想定させるものという位で，それ以上の細かいとりきめはなかったように記憶している．

　If Ⅱb type early cancer is to be defined as that variety of early cancer of the stomach which has, on macroscopic observation of its mucosal surface, no difference in height between it and the surrounding normal mucosa, it can be divided into four groups both according to whether or not it can be distinguished when seen on the surface, and also to whether or not it is flat when observed in the sectioned specimens.

　In that type of Ⅱb lesion that develops singly the size macroscopically to be detected is at least more than 5 mm in diameter. Endoscopically it may be confirmed either as discoloration, reddening, or a small bleeding spot. A Ⅱb less than 5 mm in dimensions is only determined by histological examination. Mostly it is of well differentiated nature.

　When a Ⅱb lesion is concomitantly found with other types of early cancer, it can be as large as 30 mm in diameter, mostly infiltrating the mucosa without showing itself over the mucosal surface.

Such a lesion is seen either as fading of normal mucosal color, or soft, irregular unevenness of the surface (roughness). According as a Ⅱb lesion becomes more exposed over the mucosal surface, it begins to be seen as discoloration, reddening or a bleeding spot. Such a lesion is mostly undifferentiated and has the nature of signet ring cell carcinoma.

　When a Ⅱb is accidentally found with other types of early cancer, it becomes difficult to determine its margins. Consequently, when an endoscopically suspicious area becomes less and less distinct, finally merging into the normal mucosa, it is most important to repeat biopsy at some regular distances toward the cardiac side.