胃癌側方進展範囲診断―NBI拡大内視鏡による胃癌側方進展範囲診断

Diagnosis of the Lateral Extent of Early Gastric Cancer Using Magnifying Endoscopy Combined with Narrow Band Imaging

要旨　早期胃癌の側方進展度診断を行うには，まず通常観察で病変の大まかな病変範囲を推定する．引き続きNBI拡大で，病変辺縁の粘膜表面の微細な構造と血管形態に着目して観察する．早期胃癌の病変部と健常部の構造や血管形態の違いが微細な場合もあるので，弱拡大で健常部と病変部を1視野内に入れて，相対的な整形・不整形を見比べ，その境界線（demarcation line）を全周性に観察することが重要である．早期胃癌の大部分は分化型腺癌であるため，多くはdemarcation lineを確認することで側方進展範囲を診断できる．まれに正常上皮に覆われた，粘膜固有層を手つなぎで進展する癌もあるため，生検や拡大内視鏡による質的診断を行い，特殊な癌の進展形式も頭に入れて診断する必要がある．

　The first step to determine the lateral extent of an early gastric cancer is to examine the whole lesion using white light imaging and to image the gross outline. The next step is to examine the marginal region in detail using magnifying endoscopy with NBI focusing on the microsurface structure and microvascular architecture of the mucosa. It is important to examine the tumor lesion and neighboring normal mucosa in one view in order to compare the regularity of the above-mentioned points, because the difference between the lesion and the normal mucosa is not clear in some cases. It is also important to examine the entire circumference of the demarcation line of the lesion.

　As the majority of early gastric cancers is differentiated adenocarcinoma, identifying the demarcation line of the lesion makes it possible to diagnose the extent of lateral spread in most cases. Although infrequent, some poorly differentiated adenocarcinomas spread in the lamina propria mucosae underneath the normal gastric mucosa, presecring the normal microsurface structure and microvascular architecture. On such an occasion, magnifying endoscopy is not sufficient and consideration of the results of biopsy is important to identify the margin of its lateral spread.