Epstein-Barrウイルス関連胃癌の新展開—Epstein-Barrウイルス関連リンパ球浸潤胃癌の内視鏡診断

Endoscopic Diagnosis of Epstein-Barr Virus-Associated Gastric Carcinoma

要旨●近年EBV関連胃癌は，分子生物学的特徴から免疫チェックポイント阻害薬の効果が期待されている．通常の胃癌と比較し，EBV関連胃癌はリンパ節転移の頻度が低く，予後は良好とされている．EBV関連胃癌は，胃癌全体の10％を占めており，決してまれな疾患ではなく，EBV関連胃癌を疑い，診断できることは臨床的に重要な意味を持つ．今回，当院で経験したEBV関連リンパ球浸潤胃癌33例34病変について，臨床病理学的特徴や内視鏡所見の特徴を検討した．発生部位は胃の近位部に多く，発赤調を呈する病変が多かった．表在型では0-IIc型，進行型では2，3型が主体で，粘膜下腫瘍（SMT）様の辺縁隆起を伴う症例を多く認めた．NBI拡大観察で確認できた7例8病変では，irregularとabsent MS patternが種々の程度で混在した症例が多く，MV patternはすべてirregularであったが，半数はネットワーク状の血管を形成しない蛇行の少ない不整血管を有していた．表在癌では病理組織学的深達度がT1bの症例（17/18）が多かったが，T1b癌でリンパ節転移を認めた症例はなかった．

　In recent years, EBV-GC（Epstein-Barr virus-associated gastric carcinoma）has been expected to benefit from immune checkpoint inhibitors due to its molecular biological characterization. EBV-GC has a lower frequency of lymph node metastasis and a better prognosis than common-type gastric carcinoma. EBV-GC accounts for 10% of all cases of gastric cancer, making its detection and diagnosis clinically important. In this study, we retrospectively evaluated the clinicopathological and endoscopic features of 34 lesions in 33 patients with EBV-GCLS（EBV-GC with lymphoid stroma）diagnosed in our hospital. Most lesions were located in the proximal stomach. Superficial cancers were most often type 0-IIc, and advanced cancers were types 2 and 3. Regardless of severity, most lesions had reddish depressed areas and submucosal tumor-like marginal elevations. In 8 patients with narrow-band imaging magnifying endoscopic findings, the micro-surface pattern had both irregular and absent patterns. The main microvessel patterns were fine networks comprising nonuniform polygonal shapes and unclassified vessel pattern characterized by non-tortuous irregular vessels. The histological depth of tumor invasion of superficial cancers was mostly T1b（17/18） ; however, none of the cases had lymph node metastasis in T1b cancers.