検診施設におけるHelicobacter pylori未感染胃癌の時代的変遷

Historical Changes in Cases of Gastric Cancer not Associated with Helicobacter pylori Infection, Detected at a Health Checkup Facility

要旨　Helicobacter pylori（Hp）感染歴が全くないと考えられる状態を未感染と定義すると，Hp未感染例に発生する胃癌，すなわちHp未感染胃癌は，今後Hp感染率の低下に伴って相対的に増加するものと予想される．したがって，特に胃癌検診に従事する消化器医は，その頻度や特徴についてよく理解しておく必要がある．筆者らの検討では，Hp未感染胃癌の頻度は全胃癌822例中6例（0.7％）とまれであったが，時代的変遷からみると，III期（2001～2005年）に1例（0.7％），IV期（2006～2010年）に5例（3.1％）認められており，近年において増加傾向を示していた．Hp未感染胃癌の内視鏡像は，胃角部から胃前庭部にかけての胃底腺領域内に，境界明瞭な淡い0-IIb型の褪色病変として認識されることが多い．Hp未感染例であっても油断せずにスクリーニングをすれば，その発見は比較的容易であり，極細径内視鏡でも発見は十分に可能と考えられた．今後は同病変の自然経過についての研究も必要と思われる．

　As the Helicobacter pylori（Hp）infection rate decreases, gastric cancer patients with no history of Helicobacter pylori infection “（i.e., Hp-uninfected gastric cancer）”may show a relative increase in incidence. Gastroenterologists, particularly those involved in gastric cancer screening, are therefore required to have adequate knowledge about the frequency and features of Hp-uninfected gastric cancer. In our study, the frequency of Hp-uninfected gastric cancer was quite low, accounting for 6（0.7％）of all patients with gastric cancer encountered at our facility（n＝822）. When analyzed historically, the frequency has recently increased, with 1 patient（0.7％）recorded during Period III（2001-2005）and 5（3.1％）recorded during Period IV（2006-2010）. Endoscopically, Hp-uninfected gastric cancer is often visualized as a well-demarcated color-faded dim lesion（type 0-IIb）within the fundic gland region. Its detection is relatively easy if screening is performed carefully, even in patients without Hp infection. An ultra-small diameter endoscope is also a useful tool for detecting lesions in Hp-uninfected gastric cancer. It is also necessary to study the natural course of these Hp-uninfected gastric lesions.