1）Epstein-Barr virus関連胃癌

Epstein-Barr Virus-associated Early Gastric Carcinoma

要旨　EBV関連胃癌はEBVに感染した上皮細胞がモノクローナルに増殖した腫瘍で，胃癌全体の約10％を占め，際立った臨床病理学的特徴を有する．一般の胃癌に比べ男性に多く，やや若年に発生する傾向があり，胃の近位側に好発する．内視鏡像では0 IIc型主体の例が多い．組織型はtub2（66％）ないしpor1（21％）と診断されることが多いが，特異的な組織パターンとしてlace patternとリンパ球浸潤癌が知られている．前者は粘膜内でみられることが多く，後者は粘膜下層浸潤部で認められ，結節状増殖を示す．粘液形質は特徴的に無形質か胃型形質を示す．予後良好な傾向があり，早期癌でのリンパ節転移はまれである．

　Epstein-Barr virus（EBV）-associated gastric carcinoma（GC）is a distinct subgroup of GC, comprising 10% of all cases of GC. It develops as a consequence of monoclonal growth of EBV-infected epithelial cells, which is demonstrated by in situ hybridization for EBV-encoded small RNA（EBER-ISH）. Clinical features of EBV-associated GC include male predominance, relatively younger age, preponderant location in the proximal stomach, and superficial depressed appearance in endoscopy. Histologically, EBV-associated GCs are classified mainly into tub2（66%）or por1（21%）, and they frequently display two unique histologic patterns. One is lace pattern showing irregularly anastomosing cord-like or tubular structures in the mucosal layer. The other is gastric carcinoma with lymphoid stroma which is often observed as a submucosal nodule. Most EBV-associated GCs show a null or gastric phenotype according to the expression pattern of mucin molecules（MUC5AC, MUC6, and MUC2）and CD10. EBV-associated GC shows a less frequent lymph-node involvement and a relatively favorable prognosis compared with EBV-negative GC.