内視鏡による早期胃癌のIIb進展範囲診断―NBI（narrow band imaging）拡大内視鏡の立場から

Usefulness of Magnifying Endoscopy with Narrow Band Imaging in the Determination of IIb Spreading of Early Gastric Cancer

要旨　NBI併用拡大観察後にESDを施行した早期胃癌541病変を検討した．IIb進展部は境界正診率が75.0％（18/24）と低く，慎重な範囲診断が必要である．粘膜表層で腺窩上皮様に分化を示す胃型分化型癌のIIb進展部は，色調や表面性状が周囲粘膜と類似するため，通常観察では診断困難だが，NBI拡大内視鏡を用いて，乳頭・顆粒状微細表面構造の大小不同と，ループ状微小血管の拡張像を観察することで，範囲診断が可能である．IIb進展部に微細構造の不明瞭化と複雑な屈曲，分枝を示す微小血管像を認めたときは，中～低分化型癌の進展を考えるべきである．NBI拡大診断は特殊な組織像において限界があり，IIb進展部で癌腺管が粘膜表層を置換し，非癌腺管が混在した1病変と，低異型度完全腸型癌であった1病変に対して，生検を併用した境界診断が必要であった．

　We retrospectively analyzed 541 early gastric cancers from patients who underwent endoscopic submucosal dissection（ESD）after detailed observation by magnifying endoscopy with narrow band imaging（ME-NBI）. By conventional endoscopy, it was difficult to make a correct determination of IIb spreading of differentiated-type adenocarcinoma with gastric mucin phenotype. The findings of ME-NBI were loop-form microvessels in each small granular structure（Fig. 3, 5）. The margin of this lesion could be visualized by the microvascular and fine glandular architecture different from those of the surrounding non-neoplastic mucosa. In IIb spreading of moderately or poorly differentiated-type adenocarcinoma, ME-NBI showed irregular microvessels with disappearance of the fine structure（Fig. 4）. Because ME-NBI wasn't able to clarify IIb spreading of two carcinomas : carcinoma with hyperplastic polyp（Fig. 6）and carcinoma with phenotype of complete-type intestinal metaplasia（Fig. 7）, we took biopsy specimens to determine the horizontal margin.