完全型腸上皮化生を背景に発生しWOSを伴う胃底腺粘膜型腺癌の1例

Adenocarcinoma of Gastric Fundic Mucosa Type with WOS Arising on a Background of Complete Intestinal Metaplasia, Report of a Case

要旨●患者は70歳代，男性．胃体下部小彎前壁に12mm大の発赤調で立ち上がり急峻な隆起性病変を認めた．NBI拡大観察で隆起部はWOSを伴う大小不同で小型な顆粒状・乳頭状構造を呈し，背景粘膜は絨毛状構造を呈しWGA類似の白色調変化が散見された．EMRによる一括切除を行い，病理組織学的に背景粘膜はMUC2，CD10陽性の完全型腸上皮化生，隆起部表層は主にMUC5AC陽性で腺窩上皮類似異型腺管，上皮下では不規則に分岐拡張するpepsinogen IやMUC6陽性主体の胃底腺類似異型腺管を認め，胃底腺粘膜型腺癌と診断した．また，WOSとWGA類似部分はともにadipophilin陽性の脂肪滴であり，WOSでは上皮内，WGAでは上皮下間質に存在しNBI拡大観察の血管所見を反映していた．胃底腺粘膜型腺癌の多くは萎縮のない胃底腺に発生することが多いが，本病変は背景粘膜が完全型腸上皮化生であった点，胃上皮性腫瘍にWOSを認める場合は腸型形質が多いが本病変では胃型形質であった点が貴重であると考えた．

　A male patient aged 70 years presented with an erythematous, rising, steeply elevated lesion of 12mm in size on the anterior wall of the gastric lower body. Narrow-band imaging（NBI）at magnification detected small and irregularly sized granular and papillary structures with white opaque substance（WOS）. The background mucosa was villous with scattered white globe changes similar to white globe appearance（WGA）. Histopathological examination revealed mucin 2（MUC2）and CD10-positive complete intestinal metaplasia in the background mucosa, MUC5AC-positive foveolar epithelium-like atypical ducts in the superficial layer of the tumor, and irregularly branching and dilated pepsinogen I- and MUC6-positive atypical ducts in the subepithelium, resulting in the diagnosis of adenocarcinoma of gastric fundic mucosa type. Both WOS and WGA-like areas were adipophilin-positive fatty plaques located in the epithelium in WOS and the subepithelial stroma in WGA, confirming the vascular findings on NBI magnification. Most gastric fundic mucosal adenocarcinomas originate from the gastric fundic gland without atrophy. WOS, which is observed in gastric epithelial tumors, frequently presents as an intestinal mucin phenotype. However, this lesion demonstrates a complete intestinal metaplasia of the background mucosa and exhibits a gastric mucin phenotype, which is crucial.