NBI拡大観察が有用であった散発性胃底腺ポリープ癌化の2例

Two Cases of Adenocarcinoma Occurring in Sporadic Fundic Gland Polyps Observed by Magnifying Endoscopy with Narrow Band Imaging

要旨●患者は60歳代の男性と60歳代の女性．上部消化管内視鏡検査で，胃体上部前壁に発赤調の強い小ポリープ様病変の近傍に，胃底腺ポリープと考える正色調の小ポリープを認めた．加えて萎縮のない背景胃粘膜に数個の胃底腺ポリープが散見された．2例ともHelicobacter pyloriは陰性であった．NBI拡大観察で，発赤調の強い小隆起性病変は，窩間部が開大した弧状〜楕円形の不規則な腺窩辺縁上皮内部に不整な微小血管を認め（上皮内血管パターン），分化型癌を疑った．一方，近傍の正色調のポリープは整った蜂の巣状の上皮直下毛細血管内部に楕円形の整った腺開口部を認め（血管内上皮パターン），異型のない胃底腺ポリープと考えた．診断的治療目的に，隣接する2つのポリープをESDにて一括切除した．2例とも最終病理組織診断は，発赤調の強い小ポリープ様病変は胃型（腺窩上皮型）への分化を示す超高分化腺癌で，胃底腺ポリープに発生した癌と診断された．一方，近傍の正色調ポリープは異型のない胃底腺ポリープと診断された．2例ともにプロトンポンプ阻害薬の内服歴はなく，家族性大腸腺腫症は否定的であった．NBI拡大観察が通常の胃底腺ポリープとの鑑別に有用であった，まれな散発性胃底腺ポリープからの癌化例を2例経験した．

　The patients were a 60s man and a 60s woman. Upper endoscopic examination of both the patients revealed a small, reddish polypoid lesion, adjacent to an isochromatic small polyp, believed to be a FGP（fundic gland polyp）on the anterior wall of the upper gastric body. Additionally, several FGPs were observed in the non-atrophic background mucosa. Helicobacter pylori was not found in both cases. The findings of ME-NBI（magnifying endoscopy with narrow band imaging）for the reddish polypoid lesion demonstrated an irregular MV（microvascular）architecture composed of either closed loop- or open loop-type vascular components, plus an irregular MS（microsurface structure）consisting of oval-type surface components（vessels within epithelium pattern）. In contrast, ME-NBI of the adjacent isochromatic polyp showed regularly arranged round gastric pits and honeycomb-like microvessels（epithelium within vessels pattern）. The reddish polypoid lesion was suspected to be an intramucosal adenocarcinoma of differentiated type, whereas the adjacent isochromatic polyp was a non-dysplastic FGP. We resected these two polypoid lesions by ESD（endoscopic submucosal dissection）and pathology revealed the final diagnosis of the reddish polypoid lesion as a well-differentiated adenocarcinoma occurring in FGP, whereas the adjacent isochromatic polyp was a non-dysplastic FGP. Neither of the patients had a history of using proton pump inhibitors and both denied familial adenomatous polyposis. We report two cases of adenocarcinoma occurring in sporadic FGPs, whose ME-NBI findings were useful for differentiating FGP with cancer from non-dysplastic FGP.