胃粘膜の拡大観察―早期胃癌に対する拡大内視鏡観察による分化度診断

Diagnosis of Histological Differentiation Using Magnifying Endoscopy Combined with the Narrow Band Imaging System for Early Gastric Cancer

要旨　陥凹型早期胃癌に対して狭帯域フィルター内視鏡(narrow band imaging ; NBI)システムを併用した拡大電子内視鏡観察による胃癌組織型診断の可能性について検討した．対象は2001年7月～2003年5月に拡大電子内視鏡GIF-Q240Z(オリンパス)を使用し，通常観察，NBI併用拡大観察を行った陥凹型早期胃癌141例である．粘膜微細構造の変化に加え，毛細血管像に着目して組織型と毛細血管像を検討すると，分化型癌の94例中61例(64.9％)に比較的規則的配列を示す細かな網目状の毛細血管模様が認められた(fine network pattern)．一方，未分化型癌の47例中41例(87.2％)では不規則な縮緬状の毛細血管模様が認められた(irregular corkscrew pattern)．分化型癌と未分化型癌の混在例では，両者の特徴を示す血管網が増生している像が認められた．NBI併用拡大観察により，各組織型における特徴的な毛細血管パターンが客観的に認識できることが明らかとなった．それらの特徴像を理解しておくことにより，微小病変の良悪性判定や浸潤範囲の困難な症例の正確な同定に有用となることが示唆された．

　We studied the diagnostic possibility for histological differentiation, using magnifying endoscopy combined with the narrow-band imaging (NBI) system for depressed type of early gastric cancer. This system with a magnifying endoscope yielded very clear images of the fine mucosal patterns of the gastric pits and the capillaries on the mucosal surface. The magnifying endoscopic findings for 141 lesions of depressed type of early gastric cancer were compared with the histological findings. The capillaries on the mucosal surface were classified into 2 patterns; a relatively regular fine network pattern and an irregular corkscrew pattern. It was found that 61 of 94 lesions (64.9％) with differentiated adenocarcinoma showed a relatively regular fine network pattern. On the other hand, 41 of 47 lesions (87.2％) with undifferentiated adenocarcinoma showed an irregular corkscrew pattern. Mixed lesions of differentiated and undifferentiated adenocarcinoma displayed capillary patterns of both types of cancer. The fine mucosal patterns and the features of capillary vessels, which were identified with the NBI system, correlated well with the histological differentiation. The detailed results produced by this system, and a clear understanding of the characteristics of these results, enable us to improve our ability to differentiate between benign and malignant minute lesions. Additionally, when used in conjunction with conventional endoscopic diagnosis, one is able to more accurately diagnose the extension of cancerous infiltration.