Helicobacter pylori陰性分化型早期胃癌の1例

Differentiated Type Gastric Adenocarcinoma with No Previous Helicobacter pylori Infection, Report of a Case

要旨　患者は60歳代，女性．健診の上部消化管X線造影検査で異常を指摘され，近医の上部消化管内視鏡検査で早期胃癌を認めたため，当科へ紹介され，受診となった．通常光観察では，萎縮性変化のない胃体上部前壁に20mm大の周囲と同色からやや褪色調の陥凹性病変を認めた．脱気にて病変は変形したが，ひだの集中や瘢痕所見は認めなかった．NBI拡大観察では，明瞭な境界の内部には大小不同，不均一で多様な形態の不整な微小血管と，大きさ・形状が不均一な粘膜微細表面構造を認め，胃癌と診断した．cType 0-II，cT1a，N0，M0で，ガイドライン適応病変と判断し，ESDを施行した．病理組織学的診断は，pType 0-IIc，18×18mm，tub1＞＞por，pM，UL（－），ly（－），v（－），HM0，VM0であった．MUC5ACとMUC6が陽性で，MUC2とCD10は陰性であったため，胃型の腺癌と診断された．

　A woman in her sixties had been diagnosed with a differentiated-type early gastric cancer and presented to our hospital. Anti-Helicobacter pylori antibody was negative and the patients had no history of eradication therapy. An esophagogastroduodenoscopy（EGD）revealed a 20mm depressed-type lesion in the anterior wall of the upper stomach. Helicobacter pylori-associated atrophic gastritis was not detected in the surrounding mucosa. Narrow-band imaging with magnification revealed an irregular microvessel pattern, an irregular microsurface pattern, and a demarcation line in the lesion. There was no endoscopic sign of submucosal invasion, no lymph node involvement, and no distant metastases were detected by CT scan, and the clinical stage of the cancer was determined as cT1a, N0, M0（stage IA）. The patient underwent ESD. Histological findings of the resected specimen showed that the lesion was surrounded by fundic gland mucosa without any changes suggestive of atrophy or intestinal metaplasia. The tumor was diagnosed as a Type 0-IIc, 18×18mm, intramucosal well-differentiated tubular adenocarcinoma with minimal, poor differentiation, no ulcerative findings, no lymphatic or venous invasion, and negative horizontal and vertical margins. Immunochemical staining showed that the lesion expressed gastric mucin phenotype.