大腸sm癌における浸潤度の臨床診断精度―sm浸潤距離1,000μmに対する通常内視鏡検査の診断能

Diagnostic Accuracy of the Submucosal Invasion Depth for Colorectal Submucosal Cancers, Diagnosis of Submucosal Invasion Depth 1,000μm by Conventional Colonoscopy

要旨　大腸sm癌に対する新しい内視鏡的根治基準として大腸癌研究会におけるsm癌取り扱いプロジェクト研究委員会から提唱された“sm垂直浸潤距離1,000μm未満で脈管侵襲を認めない病変”との試案に従って，sm浸潤距離の測定が可能であった290病変について通常内視鏡によるsm浸潤距離1,000μmの診断精度を検討した．隆起型sm癌156病変においてsm浸潤距離1,000μm以上の病変で出現する通常内視鏡所見は，①陥凹を認める，②緊満所見を認める，③立ち上がりが正常粘膜（Is型）であり，Ip・Isp型では62.3％，Is型では80.5％でsm浸潤距離1,000μmの鑑別が可能であった．表面型134病変のうち，表面隆起型では，①皺襞集中を認める，②緊満所見を認める，でsm浸潤距離1,000μmの診断精度は76.9％，表面陥凹型では，①緊満所見を認める，②深い陥凹，③陥凹底に凹凸を認める，で診断精度は84.1％であった．現状ではsm浸潤距離1,000μmの鑑別は通常内視鏡のみでは不十分と考えられ，正確な診断には所見の再検討または他の検査の付加が必要と考えられた．

　A new criterion for curative endoscopic treatment of submucosal cancer was proposed by the committee of “Project Study for the Treatment of Colorectal Submucosal Cancers” in the Japanese Research Society for Cancer of the Colon and Rectum. The criterion is whether or not “the lesion is of less than 1,000μm submucosal invasion depth without vessel permeation”. Focusing on this new criterion, we retrospectively reviewed 290 lesions of submucosal cancer as to whether the conventional colonoscopic findings using indigocarmine dye spray are sufficiently predictive for 1,000μmof the submucosal invasion depth. In the 156 lesions of polypoid type submucosal cancers, the presence of surface depression, expansion appearance and normal mucosa of the tumor border (in Is type) appeared with significantly high frequency among submucosal cancers with 1,000μmor more submucosal invasion depth and the accuracy rate of prediction of invasion depth was 62.3％ in Ip and Isp type, and 80.5％ in Is type. In 134 lesions of flat type submucosal cancer (IIa, nodule aggregating lesions), expansion appearance and folds converging toward the tumor appeared with significantly high frequency in submucosal cancers with 1,000μmor more submucosal invasion depth and the accuracy rate of prediction of invasion depth was 76.9％. In depressed type submucosal cancers (IIc and IIa＋IIc), the presence of expansion appearance, deep surface depression and irregular surface depression appeared significantly highly in submucosal cancers with 1,000μmor more submucosal invasion depth and the accuracy rate of prediction of invasion depth was 84.1％. Thus, using only coventional colonoscopy, the diagnostic accuracy for the differentiation of 1,000μmsubmucosal invasion depth was unsatisfactory. It will need to be reinforced with either another diagnostic modality or with a new way of predictive deduction from conventional colonoscopic findings in order to make the precise diagnosis of 1,000μmsubmucosal invasion depth.

　1) Third Department of Internal Medicine, Asahikawa Medical College, Asahikawa, Japan