術前側方進展診断が困難であった未分化型早期胃癌の1例

Difficulty of Determining Lateral Extension in Undifferentiated Early Gastric Cancer, Report of a Case

要旨　患者は70歳代，女性．早期胃癌ESD後のサーベイランス目的に施行した上部消化管内視鏡検査で，胃体下部後壁に10mm大の陥凹性病変を認め，生検にてGroup 5（sig）と診断された．白色光観察では，陥凹周囲に境界不明瞭な褪色領域を認めたが，同部位のNBI併用拡大内視鏡観察では胃炎との鑑別が困難であった．ESDにて一括切除し，病理診断では陥凹面より大きく側方進展する随伴IIb病変を認めた．陥凹面のみで癌が表面に露出しており，随伴IIb面では癌の露出は認められず，粘膜固有層から粘膜筋板近くに癌浸潤を認めた．未分化型癌では，このような進展形式のため，NBI併用拡大観察による側方進展診断が困難な例があり，白色光観察を重視し，周囲生検を必須と考える．

　A 70-year-old woman underwent upper endoscopy for surveillance after ESD（endoscopic submucosal dissection）of early gastric cancer. Endoscopic findings revealed a 10-mm depressed lesion on the posterior wall of the lower gastric body. Biopsied specimens taken from the lesion showed signet ring cell carcinoma. C-WLI（conventional white light imaging）endoscopy confirmed a discolored area in the periphery of the depressed lesion，but M-NBI（magnifying narrow-band imaging）endoscopy could not determine the margins of the carcinoma. We performed ESD of the lesion in en-bloc resection, and pathological examination of the resected specimen revealed a superficial spreading IIb lesion surrounding the depressed lesion. Cancerous cells of the IIb lesion existed in the middle or deeper layer of mucosa. Since M-NBI endoscopy cannot detect cancerous infiltration of the mucosa if the crypt structure remains intact, multiple biopsies must be taken from surrounding mucosa according to C-WLI findings especially in cases of undifferentiated carcinoma.