胃腺腫の拡大内視鏡診断

Magnifying Endoscopy of Gastric Adenoma

要旨　狭帯域フィルター内視鏡(narrow band imaging ; NBI)システムとは，面順次式電子内視鏡のRGBに従来と異なる狭帯域フィルターを用いた光源装置であり，拡大電子内視鏡との併用により粘膜微細構造および粘膜表層の毛細血管像を明瞭に描出可能である．NBI併用による拡大内視鏡観察をした胃腺腫16例と隆起型早期胃癌24例を対象に，粘膜微細構造を“small round”，“round or oval”，“tubular”，“irregular”の4パターンに，毛細血管像を血管像が不明瞭，周囲粘膜と類似の血管像，走行や形状が不規則な異常血管像の3パターンに分類して検討した．その結果，粘膜微細構造が比較的整った“small round”，“round or oval”，“tubular”の多くは組織学的に腺腫であり，粘膜微細構造に乱れのみられる“irregular”パターンおよび異常血管像の出現は悪性である確率が高いことが明らかになった．従来から言われてきた胃腺腫と隆起型早期胃癌の内視鏡的鑑別の指標に加え，NBI併用拡大内視鏡観察によって微細な所見を客観的に診断することにより病変の精緻な診断が可能なことが示唆された．

　The narrow band imaging (NBI) system is composed of a sequential electronic endoscope system and a source of light equipped with new narrow band filters corresponding to red, green and blue. This system with a magnifying endoscope was able to yield very clear images of the fine mucosal patterns of the gastric pits and the capillaries on the mucosal surface. The magnifying endoscopic findings with the NBI system for 40 lesions consisting of 16 adenomas and 24 elevated type early gastric carcinomas were compared with the histological findings. The fine mucosal patterns were classified into 4 patterns ; small round, round or oval, tubular and irregular. The capillaries on the mucosal surface were classified into 3 categories ; unclear, normal and abnormal. “Unclear” meaning the capillaries are unrecognizable,“normal” meaning the capillaries are similar to the surrounding no rmal mucosa, and “abnormal” meaning the capillaries differ from the surrounding mucosa. As a result, most lesions showing small round, round or oval or tubular patterns could be diagnosed histologically as tubular adenoma. On the other hand, the lesions showing irregular pattern and abnormal capillary shape was able to be diagnosed with a high accuracy rate as carcinoma. The fine mucosal patterns and the features of the capillary vessels, which were identified with the NBI system, correlated well with the histological diagnosis. We believe that magnifying endoscopy with the NBI system could be useful in predicting the histological diagnosis of adenoma and carcinoma used as an addition to the conventional endoscopic diagnosis.