術前の壁深達度診断が困難であった胃粘液癌の1例

Gastric Mucinous Adenocarcinoma with Difficult Preoperative Diagnosis of Invasion Depth, Report of a Case

要旨●患者は70歳代，女性．心窩部不快感を主訴に当科でEGDを施行された．白色光通常内視鏡観察で，胃体中部大彎に30mm大の口側に深い陥凹を伴う発赤調の隆起性病変を認めた．インジゴカルミン色素撒布後観察にて，口側の陥凹内部に凹凸を認め，陥凹辺縁に棘状の不整な伸びだしが観察された．一方，病変肛門側の立ち上がりはなだらかで，表面は非腫瘍粘膜に被覆された上皮下病変様の形態を呈していた．壁強伸展下観察で，口側の陥凹に収束する数条のひだ集中を認め，わずかに台状挙上を呈していたため，低確信度で台状挙上所見陽性と判定した．一方で肛門側の上皮下病変様隆起部は送気により伸展良好であった．NBI併用拡大観察で，陥凹と周囲粘膜との間に明瞭なDLを認め，陥凹内部はirregular MV pattern plus irregular MS pattern with a DLと判定し，vessel plus surface classification systemより癌と診断可能であった．病変の壁深達度の精査目的にEUSを行い，陥凹部で第3層に低エコー域を，上皮下病変様隆起部では第3層に高エコーと低エコーの混在するモザイクパターンを呈していた．以上の内視鏡所見より，粘膜下層以深へ浸潤する早期胃癌と診断し，当院外科にて腹腔鏡補助下幽門側胃切除術を施行された．切除標本では口側の陥凹は腫瘍腺管が密に増殖しており，高分化〜中分化管状腺癌を粘膜内〜固有筋層にかけて認めた．一方，肛門側の上皮下病変様隆起部には低分化腺癌および著明な粘液結節が存在し，最深部は漿膜外まで浸潤していた．術前の壁深達度診断と実際の病理組織診断に乖離を認め，壁深達度診断が困難な1例であった．

　A 70-year-old woman underwent an upper gastrointestinal endoscopy at our department due to the chief complaint of epigastric pain. White light conventional endoscopy detected an erythematous elevated lesion with a deep depression of 30mm on the mouth side in the major curvature of the middle body in the stomach. Furthermore, after dye spraying the lesion, inside of the oral side of the depression was observed to be uneven, and the depression margins were irregularly elongated, similar to spines. Conversely, the anorectal side of the lesion was gently rising, and its surface was covered with nontumor mucosa, presenting a subepithelial lesion appearance. Moreover, several folds were observed converging to the depression on the mouth side under the observation of the wall in strong extension, and the lesion exhibited a slight pedicle elevation, which was deemed to be a positive nonextension sign with low confidence. In contrast, the subepithelial lesion-like elevation on the anorectal side was well extended due to air insufflation. Magnifying endoscopy with narrow-band imaging revealed a clear demarcation line（DL）between the depression and the surrounding mucosa, and the interior of the depression exhibited an irregular microvascular pattern and an irregular microsurface pattern with a DL, indicating a vessel plus surface classification. Consequently, a cancer diagnosis was confirmed by the vessel plus surface classification system. Endoscopic ultrasonography was performed to investigate the depth of the lesion. The depressed area exhibited a hypoechoic area in the third layer, and the subepithelial lesion-like elevation exhibited a mosaic pattern with a mix of high and low echoes in the third layer. Thus, based on the abovementioned endoscopic findings, the patient was diagnosed with early gastric cancer invading deeper portion of the submucosa, and underwent laparoscopic pyloric gastrectomy at our hospital. Histopathological diagnosis of the resected specimen revealed that the depression on the mouth side was densely populated with tumor glands, and highly to moderately differentiated tubular adenocarcinoma was found from the intramucosal to the intrinsic muscularis layer. Conversely, a subepithelial lesion-like elevation was present on the anorectal side containing poorly differentiated adenocarcinoma, and a prominent mucous nodule with extraserosal invasion was present at the deepest point. In the present case, the preoperative diagnosis of the wall depth and the actual histopathological diagnosis differed, making wall depth diagnosis difficult.