内視鏡的切除適応拡大のための大腸sm癌深達度診断の検討―内視鏡を中心に

Evaluation of Endoscopic Diagnosis on Invasive Depth of Colorectal Submucosal Carcinoma, for Expansion of Indication for Endoscopic Resection

要旨　大腸sm癌に対する内視鏡切除術の適応拡大の可能性を検討する目的で，sm癌288病変の解析を行った．sm癌の肉眼型別頻度はⅠs/Ⅰspが最も多く（41％），次にⅡa＋Ⅱc（23％）であり，リンパ節転移陽性sm癌の80％がⅠs/ⅠspとⅡa＋Ⅱcであった．リンパ節転移率は4.2％（sm₁0％，sm₂6.6％，sm₃12.8％）であった．EMR後追加腸切除例の6.5％にリンパ節転移を認めた．ロジスティック回帰分析の検討では，sm深部（SM_2,3）浸潤の指標として有意な内視鏡所見は示されても，特にリンパ節転移の指標となる内視鏡所見は示されなかった．sm癌の形態計測値では，リンパ節転移陽性sm癌の最小sm浸潤値は2,300μmで，これ未満のsm浸潤値がリンパ節転移のない理論的安全域と考えられた．リンパ節転移陽性の陥凹型sm癌ではsm浸潤値は4,600μmと有意に深く，smmassiveでもsm₂程度の陥凹型sm癌に対しては内視鏡切除適応拡大の可能性が示唆された．一方，無茎隆起型sm癌についてはこのようなことは言えなかった．

　In order to evaluate the possibility of expanding the indication for endoscopic resection of colorectal submucosal (sm) carcinoma, we analyzed 288 lesions of colorectal submucosal (sm) carcinoma. Regarding the frequency of macroscopic type of those sm carcinomas, type Ⅰs/Ⅰsp was the most frequent lesion (41%) and type Ⅱa ＋ Ⅱc was the second most frequent one (23%). The rate of lymph node metastasis of those 288 lesions was 4.2% (sm₁ 0%, sm₂ 6.6%, sm₃ 12.8%). Forty-six cases underwent an additional operation after endoscopic resection mostly (91%) because of submucosal massive invasion (more than 300μm deep from the musclaris mucosae). Only 6.5% of them had lymph node metastasis, this means that, most of them had unnecessary operations (over-surgery).

　A logistic regression analysis demonstrated no significant endoscopic features of submucosal carcinoma with lymph node metastasis.

　The measurement study on H ＆ E slides of our colorectal submucosal carcinomas showed that the minimum value of submucosal invasive depth among lesions with lymph node metastasis was 2,300μm. This means that, the safety zone for escaping lymph node metastasis was theoretically less than a submucosal invasion depth of 2,300μm from the muscularis mucosae, so far as submucosal invasive depth is concerned. Moreover, concerning depressed type carcinomas, no submucosal carcinoma which had invaded less than 4,600μm had lymph node metastasis. On the contrary, the nonpedunculate exophytic type which had lymph node metastasis demonstrated the less submucosal invasion depth than the depressed type carcinoma.

　Our data suggested that it may be possibe to expand the indication for endoscopic resection of depressed type colorectal submucosal carcinoma.