非萎縮性胃底腺粘膜に発生した胃型形質の低異型度分化型胃癌の1例

Low-grade Gastric-Type Adenocarcinoma Arising in Non-atrophic Mucosa, Report of a Case

要旨●患者は70歳代，女性．上部消化管内視鏡検査で，胃穹窿部に50mm大の丈の低い隆起性病変を認めた．周囲陰性生検を7点確認のうえ，ESDを施行した．病理組織学的には萎縮の乏しい胃底腺粘膜を背景に，腺窩上皮類似の低異型度の腺管から構成される高分化型管状腺癌を認めた．粘膜下層への浸潤を認め，リンパ管侵襲が陽性であった．免疫染色で腫瘍腺管はMUC5AC陽性，MUC6陽性，MUC2陰性であり，胃型の低異型度高分化型腺癌と診断した．追加手術を施行し，腫瘍の遺残を認めた．胃型の低異型度分化型腺癌が疑われる際には，範囲診断の難しさや粘膜下層浸潤や脈管侵襲の可能性に留意した，より慎重な対応が必要と考えられた．

　A 70-year-old female underwent screening esophagogastroduodenoscopy, which revealed a 0-IIa type superficial cancer of 50mm in size on the greater curvature of the gastric fundus. Following a diagnosis of intramucosal carcinoma by white light endoscopy, endoscopic submucosal dissection was performed. The tumor margin was determined by narrow-band imaging and multiple biopsies surrounding the tumor. The pathological diagnosis was low-grade adenocarcinoma invading into the submucosal layer［tub1>pap, pT1b1（SM, 150μm）, ly1, v0, pHMX, pVMX］. The tumor had a gastric-predominant mucin phenotype. Additional surgery revealed residual intramucosal tumor in the surgically resected specimen.

　Low-grade gastric-type adenocarcinoma may have a higher risk of submucosal invasion or lymphovascular invasion than high-grade or intestinal-type adenocarcinoma, and it may be more difficult to decide the margin of the lesion. Therefore, we must be careful before performing endoscopic resection for such lesions.