大腸sm癌に対する内視鏡的切除の可能性と危険性―特にsm癌深達度細分類からみて

Indication for Endoscopic Resection of Submucosal Colo-rectal Cancer, with Special Reference to the Grade of Invasion of the Submucosa

要旨　粘膜下層を3等分する相対分類は簡明で実用的であるが，sm₁癌のリンパ節転移率はsm₂以深癌と差がみられず，内視鏡治療との関連からみると問題があり，sm₁癌については粘膜筋板からの垂直方向距離を測定し，500μm以内をsm_1s，（shallow），それ以深をsm_1d（deep）として検討した．その結果，高分化型癌でsm_1s，であれば，リンパ節・リンパ管・先進部簇出・先進部組織型の高異型化はみられず，細分類の観点からみた内視鏡的切除の適応はsm_1s（500μmまで）が，現時点では妥当であると考えられた．

　A simple and convenient classification can be made by dividing the grade of invasion of the submucosa (sm) of colo-rectal cancer into three levels, i.e., sm₁ ; limited within one third from the muscularis mucosae, sm₂ ; limited within two thirds from the muscularis mucosae, sm₃ ; invading beyond sm₂. However, there are some problems with the above classification. The major one is that there are no statistical differences between sm₁ and sm₂ cancer in lymph node metastasis rate. Resolving the problem, we evaluated histopathologically 29 lesions of sm₁ cancers which were surgically or endoscopically resected from 1990 to June 1998.

　As a result, it was noted that lymph node metastasis, lymphatic vessel invasion or tumor budding at the part ahead of the cancer front were found in well-differentiated sm₁ cancers limited within 500μm from the muscularis mucosae. Therefore, we have been dividing the grade of sm₁ into sm_1s (shallow) -limited within 500μm from the muscularis mucosae and sm_1d (deep) -advancing over 500μm.

　From a view point of grade of colo-rectal sm cancer, well-differentiated sm_1s, cancer can be treated appropriately by endoscopic resection alone.