自己免疫性胃炎を背景とした胃癌の臨床病理学的特徴

Clinicopathological Characteristics of Gastric Cancer Associated with Autoimmune Gastritis

要旨●自己免疫性胃炎（AIG）は，本邦ではまれな疾患とされてきたが，近年報告例が増加している．内視鏡所見または病理所見からAIGを診断することは，特にH. pylori感染合併例では困難な場合がある．また，AIG合併胃癌の詳細な特徴については解明されていない．今回，当院で経験したAIG 86例（うち胃癌合併35例，46病変）を遡及的に検討した．AIG合併胃癌は，隆起型の分化型早期胃癌が典型とされているが，当院では，肉眼型は0-IIcが最も多く39.1%を占め，組織型では未分化型癌が28.3%，進行癌も19.6%と比較的多くみられ，既報と相違があった．AIGの診断契機に関しては，内視鏡所見からAIGを診断できずに，病理所見からAIGの診断に至った症例が36.0%を占めた．特に胃癌合併例では，65.7%が病理診断契機となっており，病理診断の有用性が示された．また，H. pylori感染例では内視鏡所見からAIGを診断できたのは約半数のみであり，AIGにH. pylori感染が加わると，AIGの内視鏡診断が困難になる可能性が示唆された．

　AIG（autoimmune gastritis）is a rare disease in Japan ; however its prevalence has been increasing in recent years. Diagnosing AIG from endoscopic or pathological findings can be difficult, especially if a Helicobacter pylori infection is also present. The detailed characteristics of AIG-associated gastric cancer have not been elucidated. In this study, 86 cases of AIG（including 35 cases with gastric cancer, 46 lesions）diagnosed in our hospital were retrospectively reviewed. The typical AIG-associated gastric cancer has been reported as an elevated type of the differentiated-type early gastric cancer. However, contradictory to previous reports, our data demonstrated the most common gross type to be 0-IIc（39.1%）and the prevalence of undifferentiated carcinoma and advanced carcinoma was observed to be relatively common（28.3% and 19.6%, respectively）. With respect to the diagnosis of AIG, 36.0% of the cases were diagnosed from pathological findings and the diagnosis could not be made from endoscopic findings. 65.7% of cases with gastric cancer were diagnosed based on pathological findings, highlighting the efficacy of pathological diagnosis. In patients with H. pylori infection, AIG could endoscopically diagnosed in only about half of the cases, suggesting that endoscopic diagnosis of AIG might be more difficult in the presence of an H. pylori infection.