大腸癌研究会によるⅠp・Ⅰsp型大腸癌浸潤度判定の基準

The Criteria for Grading Ⅰp・Ⅰsp Type Submucosal Invasive Colorectal Carcinomas, Tentatively Decided by the Japanese Society for Cancer of the Colon and Rectum

要旨　大腸sm癌浸潤度測定においては，①癌の粘膜下層への浸潤により粘膜筋板が不明瞭化あるいは消失しているため粘膜内癌部と粘膜下層浸潤部との境界線が容易に判定できない病変をどのように測定するか，②形態の異なる腫瘍のsm浸潤度をどのように測定するかという問題点が挙げられる．特にⅠp・Ⅰsp型大腸sm癌では，粘膜筋板が錯綜しているためにその同定が困難であり，さらにその形態から表面型腫瘍に比較し浸潤度が大きく測定されてしまう．大腸癌研究会sm癌プロジェクトではこれらの問題点を解決するため，浸潤度測定に際して，粘膜筋板をその状態から5つのタイプに分類し，Ⅰp・Ⅰsp型については，head invasionを考慮に入れて基準線の設定を行い，浸潤度測定の統一化を試み，多施設にて浸潤度とリンパ節転移との関連を調査中である．この測定方法に準拠して当科のⅠp・Ⅰsp型sm癌61例について浸潤度測定を行った．リンパ節転移陽性群と陰性群でsm浸潤値に有意差を認め，転移陽性群のsm浸潤最小値は1,400ymで，head invasion症例にはリンパ節転移を認めなかった．今後，多施設調査の結果をもとに有用な浸潤度測定方法を確立し，リンパ節転移との関連を明らかにする予定である．

　In grading submucosal invasive colorectal carcinomas based on their depth, there are problems in recognizing the muscularis mucosae when it is obscure or has disappeared because of the infiltration of cancer cells. There are alse problems in measuring the depth of different macroscopic types of tumors, compared with superficial type colorectal carcinoma, in Ⅰp・Ⅰsp type colorectal carcinomas especially, it is difficult to recognize their muscularis mucosae because it is often complicated and the depth of submucosal invasion is often over-estimated.

　To resolve these problems, the Japanese Society for Cancer of the Colon and Rectum has been attempting to determine criteria for grading submucosal invasive colorectal carcinomas on the basis of their depth of invasion characteristic of these criteria is the fact that the muscularis mucosae is classified into five types. Also two different methods of measuring the depth of submucosal invasion is proposed for the grading of two major macroscopic types, viz. Pedenculated and superficial types.

　We measured the depth of submucosal invasion of 61 cases of Ⅰp・Ⅰsp type submucosal invasive colorectal carcinomas using the above criteria and investigated the correlation between lymph node metastasis and the depth. The depth of submucosal invasion was significantly deeper among lesions with lymph node metastasis than those without lymph node metastasis. The minimum depth among the lesions with lymph node metastasis was 1,400μm and cases of head invasion had no lymph node metastasis.

　More data will be needed in order to decide whether these criteria will be useful for the grading of submucosal invasive colorectal carcinomas. At present, the Japanese Society for Cancer of the Colon and Rectum is analyzing much data from several facilities, and clarifying the correlation between lymph node metastasis and the depth of submucosal invasion.