胃分化型SM1癌（垂直浸潤500μm未満）の診断―500μm以上と対比して―ひだ集中のある陥凹型早期胃癌における内視鏡診断（未分化型癌も検討に含めて）

Diagnosis of SM1 Differentiated Type Early Gastric Cancer (Penetrates into the Submucosa Less than 500μm)―Compared with SM2 Early Gastric Cancer (Penetrates into the Submucosa over 500μm) : Endoscopic Diagnosis of Depressed Type Early Gastric Cancer with Converging Folds

要旨　集中皺襞を伴うSM1癌(粘膜筋板下端から垂直浸潤500μm未満)とSM2癌(垂直浸潤500μm以上)とを比較すると，先太りならびに癒合所見はSM2癌に有意に多く，これらの所見が癌のsm浸潤(癒合はM癌では認められないことを以前報告済み¹⁾)，特にsm深層への浸潤に伴って出現する所見であることが示唆される．また，SM1癌とSM2癌の肉眼所見を比較すると，SM2癌において病変部の厚みが目立ち，この所見は送気量を減らしたときに特に強調される．これは病理組織学的には，癌が500μmを超えてsm深層に浸潤すると，浸潤する腫瘍量や反応性に出現する線維組織量が増えるためと考えられ，病変部におけるsm層の厚みが2,000μmを超える早期胃癌の約75％がSM2癌であった．したがって，超音波内視鏡(EUS)により病変部sm層の厚みを計測することで，間接的に癌のsm浸潤深度の鑑別が可能となると考えられる．

　In comparing SM1 gastric cancer (the depth of submucosal penetration less than 500μm) with SM2 gastric cancer (the depth of submucosal penetration over 500μm) with converging folds, clubbing and fusion of the converging folds, which is often seen in SM2 gastric cancer (we already reported that the fusion of the converging folds could not be found in M gastric cancer), we were made to think that these shapes of the converging folds appear when cancer penetrates into the submucosa, especially into the deep layer of the submucosa. Furthermore the thickness of the lesion is more typical in SM2 gastric cancer compared with SM1 gastric cancer and this appearance is emphasized by decreasing air infusion. From pathological findings, this thickening is because, when gastric cancer penetrates into the submucosa over 500μm, the volume of cancer and the reactive fibrosis increases. 75％ of gastric cancers with submucosal thickness over 2,000μm are SM2 gastric cancers. Because of this we are thinking that it might be possible to make a differential diagnosis of SM1 and SM2 gastric cancer by measuring the thickness of the submucosa using endoscopic ultrasonography.