範囲診断が困難であった分化型管状腺癌と低分化腺癌の衝突癌

Gastric Synchronous Adenocarcinoma with a Difficult Endoscopic Diagnosis, Report of a Case

要旨●患者は80歳代，男性．除菌後胃炎を背景として胃体下部前壁に約20mm大の境界不明瞭な発赤調陥凹性病変を認め，NBIではbrownish areaを呈した．ME-NBIにて，表面構造の違いで境界明瞭であった．除菌後の粘膜内高分化管状腺癌と診断しESDを施行した．病理組織学的には粘膜内高〜中分化管状腺癌で，辺縁のわずかな範囲で表層非腫瘍であった．また，この病変と一部重なって肛門側前壁側に胃底腺深部に進展した術前未診断の粘膜内低分化腺癌があり，側方断端陽性となった．通常，低分化腺癌は腺頸部に存在するが，本例では粘膜筋板直上のみに存在していた．粘膜中〜表層は胃底腺粘膜が保たれており，同部位のME-NBIは背景粘膜と同様の整な腺管構造を呈していたことから，内視鏡診断の限界例と判断した．このような症例では再発リスクが高いため，正確なマッピングと内視鏡像との対比に基づいて再発予測部位を同定し，サーベイランス内視鏡時に詳細に観察することが重要である．

　The patient was an 80-year-old man with post-eradication gastritis. A 20-mm reddish depressed lesion with an unclear margin was located at the anterior wall of the lower gastric body. Narrow-band imaging revealed a brownish area, and magnification endoscopy with narrow-band imaging revealed clear margin, which was identified by the difference in surface patterns. Endoscopic diagnosis revealed well-differentiated adenocarcinoma of the mucosa. Endoscopic submucosal dissection was performed, and histological diagnosis revealed T1a stage, which represents a well to moderately differentiated adenocarcinoma. Only a small peripheral part of the adenocarcinoma was covered with non-neoplastic epithelium. In addition, an unexpected poorly differentiated adenocarcinoma of the mucosa was identified on the anterior anal side, and it was overlapping with the main lesion. It spread laterally in the deep mucosal layer under the fundic gland and reached the edge of the specimen. Usually, poorly differentiated adenocarcinoma spreads to the middle or superficial layer of the mucosa. However, this poorly differentiated adenocarcinoma was found only in the deep mucosal layer just above the muscularis mucosa, and the normal fundic gland was maintained above the cancerous lesion. Therefore, it was impossible to diagnose this lesion by endoscopy because the surface pattern was regular and similar to the background mucosa.

　Such a case has an extremely high risk of local recurrence. Therefore, it is important to predict the recurrence based on the comparison between the accurate mapping and endoscope image, for the surveillance endoscopy.