術前診断が困難であった低異型度分化型進行胃癌の1例

Extremely Well-Differentiated Adenocarcinoma of the Stomach, Report of a Case

要旨　患者は51歳，男性．主訴は下血．出血源の精査目的で上下部消化管内視鏡検査を施行した．下部消化管内視鏡検査では上行結腸に憩室を認め，憩室出血と診断した．また同時に行った上部消化管内視鏡検査で，胃体中部大彎やや前壁寄りに0-IIa＋IIc病変を認めた．陥凹面は発赤調の顆粒状粘膜を呈し，陥凹部周囲は粘膜下腫瘤様に隆起していた．悪性腫瘍を疑ったが，生検組織の病理組織学的所見はGroup IIIで悪性とは判定できなかった．そこで，1週間後に再検査を行ったところ，NBIによる拡大内視鏡検査で陥凹部の微小血管構造と表面微細構造に軽度の乱れがあり，深達度がSMの高分化腺癌を疑った．2回目の生検でGroup IVと診断されたため，病変に対して幽門側胃亜全摘術を施行した．切除標本による病理学的所見では，表面に露出している病変よりもSM層に広く浸潤する形態の低異型度腺癌であった．

　A 51-year-old man was admitted to our hospital for melena in December, 2008. Though the melena would ordinarily be caused by bleeding from the diverticulum of the ascending colon, we accidentally found by upper gastrointestinal endoscopy, a thick 0-IIa＋IIc-like lesion with fold convergence at the anterior wall of the stomach body area. This gastric lesion also looked like a submucosal tumor because its surface was covered with normal mucosa. but, due to endoscopic findings and NBI observations, we suspected that the lesion was a malignant tumor. However, the first histological analysis using biopsy reported an unexpected result ; Group III. We carried out gastroduodenal endoscopy again, and the secondary biopsy examination resulted in Group IV. We strongly suspected the tumor to be malignant, so subtotal gastrectomy was performed. The final pathological diagnosis was very well-differentiated adenocarcinoma invading to the muscularis propria. The carcinoma cells had crawled under the normal mucosa epithelia.