ESDで広範囲切除断端陽性となった未分化型胃癌の1例

Magnifying Endoscopy with Narrow-Band Imaging Fails to Diagnose the Extent of Undifferentiated Type of Early Gastric Cancer, Report of a Case

要旨●患者は80歳代後半，女性．主訴はなし．糖尿病で通院加療中であったが，健診目的で施行した上部消化管内視鏡検査で異常を指摘された．胃体下部前壁に比較的明瞭な境界を有する陥凹性病変を認め，早期胃癌0-IIc型と診断され，陥凹部からの生検では印環細胞癌が証明された．NBI拡大観察では，病変中央部の陥凹に一致しcorkscrew patternを認め，陥凹周囲の粘膜には異常を指摘し得なかった．高齢であるため十分なインフォームドコンセントを行ったうえでESDを施行した．十分なフリーマージンを確保してESDを施行したが，切除病理組織では病変中央の陥凹部では印環細胞癌が粘膜全層に，陥凹周囲では正常上皮を残しながら粘膜中層以深を癌が浸潤したため，術前のNBI観察では水平方向への病変の拡がりを捉えることができなかった〔gastric cancer Type 0-IIc＋IIb，UL（−），sig，por2，pT1b2（SM2：1,000μm），ly1，v0，INFc，int，HM1，VM0）〕．NBI併用拡大内視鏡検査にも限界があり，通常内視鏡検査を軸とした総合的な所見および症例に応じて術前の病変周囲からの陰性生検による確定診断が必要不可欠であると考えられた．

　An 80-year-old woman with an abnormality of the stomach underwent esophagogastroduodenoscopy, which revealed a depressed lesion on the anterior wall of the lower body of the stomach. Biopsy of the depressed lesion revealed an undifferentiated adenocarcinoma（signet ring cell carcinoma）, and we thus diagnosed the patient with early gastric cancer type 0-IIc. Magnifying endoscopy with narrow-band imaging revealed the corkscrew pattern in the depression; however, we could not observe the remarkable changes in the microsurface/microvascular pattern in the surrounding mucosa. Microscopic examination of the resected specimen revealed that the tumor in the depressed lesion（IIc）consisted of undifferentiated adenocarcinoma（por, sig）, which had invaded the submucosal layer with full-layer invasion of the mucosa. In the surrounding mucosa of the IIc lesion, undifferentiated adenocarcinoma had invaded the mid- to deep part of the mucosa with normal epithelium［gastric cancer 0-IIc＋IIb, UL（−）, sig, por2, pT1b2（SM2 : 1,000μm）, ly1, v0, INFc, int, HM1, VM0］.

　In undifferentiated type early gastric cancer, if the surface pattern is intact, the extent of cancerous infiltration in the mucosa cannot be identified using magnifying endoscopy. In such cases, biopsies of the surrounding mucosa should be performed.