特徴的な超音波像を呈した胃アニサキス性好酸球性肉芽腫の1例

Eosinophilic Granuloma with Characteristic EUS Image in Gastric Anisakidosis, Report of a Case

要旨●患者は50歳代，男性．検診の上部消化管内視鏡検査にて胃角部前壁に約10mm大のSMTを認めた．超音波内視鏡（EUS）では比較的均一な低エコー腫瘤であり，その中央部に楕円形で高エコー輝度の構造物が確認された．11か月前には異常を認めないことが確認されたが診断に至らず，確定診断目的にESDを施行した．粘膜下層に寄生虫とみられる線状の異物を認め，密な炎症細胞浸潤とリンパ濾胞から成る腫瘤を認めた．無症状であったことから緩和型の胃アニサキス症による好酸球性肉芽腫と最終診断された．EUSで認めたcentral hyperechogramは胃アニサキス好酸球性肉芽腫の特徴的所見とされており，これを認識することはunnecessary surgeryを防ぐためにも極めて重要と考えられる．

　A male in his 50's with a gastric SMT presented for a health checkup. Gastrography and gastroscopy revealed a small SMT, 10mm in size, in the anterior wall of the angle. Endoscopic ultrasonography revealed a hypoechoic mass with central hyperechogram. No SMT lesion was detected in the gastric angle on previous EGDs. ESD was performed for definitive diagnosis. Histological findings revealed an inflammatory mass with lymphoid follicles and Anisakis larvae in the submucosal layer. This granuloma comprised numerous eosinophils and lymphocytes. Our patient exhibited no symptoms ; thus, he was diagnosed with a mild form of anisakidosis. The central hyperechoic region corresponded to the bodies of the Anisakis mites and is a characteristic finding in gastric anisakidosis granulomas. It is important to completely recognize the central hyperechogenicity within the hypoechoic mass on EUS to avoid unnecessary surgery.