大腸腫瘍性病変の臨床病理学的特性からみた内視鏡治療の適応と実際―スネアEMRの観点から

Adaptation of Endoscopic Treatment from the Viewpoint of Clinico-pathological Feature in Colorectal Neoplasm

要旨　大腸腫瘍性病変に対する内視鏡治療は，内視鏡的粘膜切除術（EMR）が主流で，最近では腫瘍径が大きな病変に対して内視鏡的粘膜下層剥離術（ESD）が大腸にも適用されつつあるが，治療適応としての病変の臨床病理学的特性を理解することが重要である．当センターにて経験した大腸腺腫・早期癌7,909病変において，腫瘍径20mm以上の病変が占める割合は5.1％に過ぎず，LSTを含む平坦型病変が主体で，担癌率は44.5％，sm癌率は16.1％であった．LSTに対する治療法の検討では20mm以下の病変ではEMRが行われていたが，25～29mmではEPMR，30mm以上では外科的切除がなされ，スネアによる一括切除の限界は20mm以下と判断した．LSTを4つに亜分類した臨床病理学的検討では腫瘍径の増大に比例して担癌率・SM癌率が上昇したが，特にG-M群とNG-PD群では腫瘍径20mm以上の悪性度が非常に高かった．またLSTにおけるSM深部浸潤癌は61.8％と腫瘍径とは無関係に高く，脈管侵襲率も67.6％と高かった．以上よりスネアによるEMR一括切除の限界は20mmにあるが，それ以上の腫瘍径の病変に対する内視鏡治療の適応を考えた場合，SM癌率，SM深部浸潤癌率，脈管侵襲率の検討より内視鏡治療だけでは完結しえない可能性が高いと結論し，病理学的評価が正確にできる切除の必要性が求められる．

　In endoscopic treatment for colorectal neoplasm, we have mainly used endoscopic mucosal resection (EMR). Recently, we have been using the endoscopic sub-mucosal dissection method (ESD) for larger-sized neoplasms. From the viewpoint of adaptation, we should recognize and understand the clinico-pathological peculiarities of these lesions. We investigated 7,909 colorectal neoplasms, which were excised by endoscopic and surgical treatment in our institute. Only 5.1％ of these were over 20mm, and the early cancer rate was 44.5 and the invasive cancer rate was 16.1％. On the other hand, we inspected 955 LST lesions concerning treatment methods, invasive cancer rate, and invasion of vessels. Of treatment methods, we chose the en-bloc EMR method for the lesions of LST under 20mm. 25～29mm lesions were resected piecemeal using EPMR method, and lesions of over 30mm were operated on surgically. In the over 20mm LST lesions, the deep invasive cancer rate was 61.8％, and vessel invasion was 67.6％. In conclusion, we considered that 20mm was the size limit of lesions suitable for en-bloc EMR. We can't carry out the EMR method for perfectly lesions over 20mm, because their invasive cancer rate, deep invading rate, and vessel invading rate is very high. If we try to use endoscope treatment for lesions over 20mm, we must resect specimens that will stand up perfectly to clinico-patological examination.