H. pylori未感染胃癌─現状と未来の課題

Characteristics of Gastric Cancer without Helicobacter pylori Infection and its Relation to Background Mucosa

要旨●H. pylori（Helicobacter pylori）感染率の低下を背景に，従来まれとされたH. pylori未感染胃癌は今後相対的に増加が予想される．今回2005年4月〜2017年10月の期間に経験した，H. pylori未感染胃癌を部位別，組織型別に考察した．内視鏡診断，感染診断，組織学的診断のすべてにおいてH. pylori未感染と考えられた対象症例は50例，うち胃噴門部・食道胃接合部腺癌10例，胃体上部を中心に胃底腺領域に局在した胃型形質を有する超高分化型（低異型度）腺癌16例，胃底腺と幽門腺の境界領域に局在した印環細胞癌22例，体部4型1例，幽門前庭部3型1例で，大部分が早期癌しかも粘膜癌であった．H. pylori未感染胃癌においても腺領域ごとに好発する病変の形態や組織型に特徴があることが示唆された．

　We retrospectively investigated patients with gastric cancer without H. pylori（Helicobacter pylori）infection from April 2005 to October 2017. In this study, 50 patients who met the requirement of not being infected by H. pylori in detection diagnosis and endoscopic and histological examinations were enrolled.

　Interestingly, most patients could be classified into three categories. First, in 10 patients, cancer was located at the gastric cardia or gastroesophageal junction. Second, in 16 patients, very well-differentiated adenocarcinomas, all of which were superficial cancers, were located in the fundic gland region. Pathologically, the appearance and immunohistochemical phenotype resembled the foveolar epithelium, fundic gland, pseudopyloric gland, or a composite of them. Third, in 22 patients, signet-ring cell carcinoma was located in the transitional zone of fundic and pyloric glands. Most of them were flat whitish lesions restricted to the mucosa.

　Our study indicated that gastric cancer without H. pylori infection can be classified into at least three distinct categories closely related to the gastric region and background mucosa.