UL陰性未分化型胃粘膜内癌・粘膜内側方進展のNBI併用拡大内視鏡診断―その可能性と限界

The Possibility and Limitation of Magnifying Endoscopic Diagnosis Using NBI in the Extent of Undifferentiated Intramucosal Gastric Adenocarcinoma

要旨　未分化型胃粘膜内癌・粘膜内側方進展のNBI併用拡大内視鏡像と，その範囲診断の可能性と限界について検討した．対象は2006年1月～2007年10月に当院で手術した未分化型早期胃癌12病変である．口側粘膜内進展境界をNBI併用拡大観察で診断してクリップでマーキングし，外科的手術後，その部位の組織像を検討した．検討部位は33部位であった．粘膜内進展は 組織学的に①癌が表面に露出している病変（16部位），②非癌上皮が表層を覆っているも腺窩の部分が癌で破壊されている病変（10部位），③粘膜の構造を保持したまま腺頸部を癌が浸潤している病変（4部位），④腺窩上皮には浸潤がなく粘膜固有層にのみ癌が浸潤している病変（3部位）に分類された．正診は③ 15/16（93.8％），② 8/10（80％），③ 0/4（0％），④ 2/3（66.7％）であった．それぞれの拡大像は，①はcorkscrew状血管像，②はdestructive structure sign と fine wavy microvessels pattern が特徴で不連続に続くことも多かった．③は胃炎と同様の血管・粘膜構造であり，④では粘膜模様内に太めの螺旋状血管が観察された．癌が露出した場合と非癌上皮に覆われていても腺窩が癌によって破壊されている場合は，NBI併用拡大で診断できる可能性が高かったが，非癌粘膜の腺窩構造を保ったまま腺頸部を癌が浸潤する進展形式では，NBI併用拡大観察による診断は不可能と考えられた．

　To examine whether magnifying endoscopy using NBI is practical or not in diagnosis of the extent of intramucosalundifferentiated gastric adenocarcinomas, thirteen superficial-type gastric undifferentiated adenocarcinomas were observed by magnifying endoscopy using NBI and the proximal border of the cancer was diagnosed and marked with clips at two or three points before surgical operation（Jan. 2006 to Oct. 2007）. After surgical resection, the clips were removed and indigocarmine was injected at the marking points. Histological specimens were then prepared using the marking points as a guide, and the histological features were examined and compared with the magnified views using NBI.

　Histological patterns were divided into four types ; A. Exposure of the undifferentiated adenocarcinoma : B. Retention of the non-cancerous surface epithelium with destruction of crypt structure by cancer infiltration : C. Retention of the non-cancerous surface epithelium and structure with infiltration of cancer cells : D. Retention of the non-cancerous mucosa with cancerous infiltration into the proper mucosal layer. The rate of accurate diagnosis was 93.8％（15/16）for type A, 80％（8/10）for type B, 0％（0/4）for type C and 66.7％（2/3）for type D. Accuracy was significantly higher for types A and B than for type C. Magnified observation of type A showed acorkscrew microvascular pattern and no surface mucosal pattern, whereas that of type B showed partial disappearance of slit-like and branched pits in gastritis and fine wavy microvessels pattern. Magnified observation of type C showed a gastritis-type microvessel pattern and that of type D showed thick wavy microvessels pattern.

　Undifferentiated cancer can be discriminated by magnifying endoscopy if cancerous cells are exposed or if the structure of crypts has been destroyed by cancer cells. However, magnifying endoscopy cannot recognize cancerous infiltration into the mucosa if the structure of crypts is still intact.