PG type隆起型大腸T1癌のSM浸潤距離測定の実際

Actual Assessment of the Depth of Submucosal Invasion of PG（polypoid growth）type Protruded Colorectal T1 Carcinoma

要旨●PG type隆起型大腸T1癌では，粘膜筋板の走行推定ができない病変や粘膜筋板消失例でもSM浸潤距離測定部位に粘膜内病変が残存するものが多く，その厚さは平均で1,200〜1,300μm前後と推定された．したがって，現行のSM浸潤距離測定法を用いた場合，SM浸潤距離にはこれら粘膜内病変の厚さが加算されている可能性がある．PG type大腸T1癌の辺縁部には，大部分で丈の高い粘膜内病変が残存していたことから，正確なSM浸潤度判定を行うためには，臨床画像検査では病変辺縁部の所見に注目し，PG typeかどうかを鑑別することが有用と考えられる．

　In PG-type protruded colorectal T1 carcinoma, the residual intramucosal part of the tumor is usually present, even without possible identification of the muscularis mucosae at the site of submucosal invasion. The average width of the residual intramucosal part is estimated to be 1,200〜1,300μm, indicating that the width of the residual intramucosal part might be included in the depth of submucosal invasion assessed according to the present rules. For the clinical assessment of the depth of submucosal invasion of protruded T1 colorectal carcinoma, it is useful to determine whether the tumor is PG type by focusing on the periphery of the tumor, as most PG-type protruded colorectal T1 carcinomas have a protruding residual intramucosal part at the periphery.