完全摘除生検可能な大腸T1（SM）深部浸潤癌の術前診断―拡大内視鏡（IEE）

Endoscopic Diagnosis by Magnifying Image-enhanced Endoscopy of SM-deep Infiltrating Colon Cancer in Which a Complete Endoscopic Resection is Possible

要旨　内視鏡的完全摘除生検が可能な大腸SM癌について，IEEによる術前診断上の特徴を明らかにする目的で検討を行った．本検討では，内視鏡的に垂直断端陰性で切除された病変，および外科的切除された病変のうち，SM癌最深部と固有筋層上縁との距離が1,000μm以上の病変（SM1およびSM2）について，内視鏡的完全摘除生検が可能な大腸SM癌と定義した．NBI拡大観察分類については，広島分類を使用した．結果は，大腸SM癌46病変のうち，Type BおよびC1を呈した13病変は全例SM1またはSM2であった．Type C2を示した26病変のうち，Type C2の領域の長径が10mm以下の20病変の全例がSM1またはSM2であり，10mmを超えた6病変のうち4病変がSM1またはSM2で2病変がSM3であった．Type C3を呈した7病変については，SM2が1病変でSM3が6病変であった．大腸SM癌の術前IEE診断において，Type C3を呈する病変は内視鏡的完全摘除生検が困難な病変と考えられた．Type C2においては多くが完全摘除生検可能であったが，Type C2の領域の長径が10mmを超えると完全摘除生検が困難な病変もみられた．

　We aimed to clarify the preoperative diagnosis of colon cancer with submucosal invasion（colon SM cancer）in which complete, endoscopic, en bloc resection is possible using IEE（image-enhanced endoscopy）. In this study, colon SM cancers in which complete, endoscopic, en bloc resection was possible were defined as lesions for which the distance from the forward tip of the SM layer infiltration and the muscle layer was≧1,000μm（SM1 and SM2）. For IEE, we used the NBI Hiroshima Classification. There were 46 colon SM cancer lesions ; 13 of these lesions that were classified as type B and C1 were all SM1 or SM2. Among the lesions classified as type C2（26 lesions）, the major axis in the type C2 areas was≦10mm in 20 lesions ; among the six lesions that exceeded 10mm, four were SM1 or SM2 and two were SM3. There were seven type C3 lesions ; one was SM2 and six were SM3. In endoscopic diagnosis of colon SM cancer, lesions of Type C3 are lesions in which endoscopic, complete, en bloc resection is difficult, and with Type C2 also, when the major axis exceeds 10mm in size, it is an indication that the lesion will be one for which performing complete, en bloc resection will be difficult.