3）0 IIb型

Early Gastric Cancer, Type 0 IIb

要旨　IIb型早期胃癌はその定義と頻度の低さから臨床的には診断困難な癌とされている． 胃癌取扱い規約では，IIb（表面平坦型）を正常粘膜にみられる凹凸を超えるほどの隆起・陥凹が認められないものと定義し，臨床所見，手術所見，病理所見の3者をそれぞれの時期に判定して，総合所見により記載するものとしている．しかし，どの時期を有意にとって最終的に総合所見とすればよいのかという記載がなく，臨床重視の立場，病理重視の立場，総合的な立場から，それぞれの定義が提唱されており，混乱の原因となっている．提示した2症例ともに通常内視鏡検査が発見の契機となっており，引き続き行った色素内視鏡検査，NBI拡大内視鏡検査で病変が明瞭となっている．臨床の立場からは，X線検査では病変の描出は撮影された二重造影像の質に左右されること，内視鏡切除例が増えていること，固定の方法にも問題があると思われることから，IIb型の肉眼分類は内視鏡検査で判定すると取り決めれば，混乱は少なくなるものと思われる．

　Early gastric cancer, type 0 IIb is regarded as a carcinoma difficult to diagnose clinically due to the ambiguity of the definition and its rarity. In the Japanese classification of gastric carcinoma, type 0 IIb（superficial flat type）is defined as a lesion devoid of any elevation or depression exceeding the extent of irregularity as recognized in the normal gastric mucosa, and the gross type is to be described as a comprehensive finding based on clinical, surgical, and pathological findings.

　However, owing to the lack of a description in the classification about which findings should be given most consideration, different definitions have been proposed respectively from each standpoint, and have caused confusion regarding the definition of type 0 IIb. In roentogenography, delineation of the lesion depends on the quality of the double contrast study. Both of the cases presented in our article were picked up by conventional endoscopy, and dye spraying endoscopy and magnified endoscopy with narrow band imaging（NBI）clearly outlined the lesion. From the clinical standpoint, taking into account the increase of endoscopic resection and the effect of matching procedures to gross appearance, we consider that the confusion regarding the definition would be settled by agreement that the gross classification of type 0 IIb should be judged by its endoscopic findings.