大腸SM癌のリンパ節転移に関する病理学的因子の研究―組織型の評価を中心に

Analysis of Pathological Risk Factors for Lymph Node Metastasis of Submucosal Invasive Colon Cancer

要旨　外科的に切除された大腸粘膜下層浸潤癌（大腸SM癌）182例を対象に，SM浸潤部の病理学的因子とリンパ節転移の有無との関連をロジスティック回帰分析を用いて検討した．リンパ節転移症例は17例（9.3％）であった．単変量解析ではリンパ節転移と有意な相関を示したのはリンパ管侵襲，リンパ球浸潤，篩状構造，静脈侵襲，浸潤距離であった．ただし，リンパ球浸潤は負の相関を示した．多変量解析による，リンパ節転移の危険因子としての重要度は，前記の順序であった．単変量解析のOdds比の検討から，リンパ節転移の危険性の目安となる基準のSM浸潤距離は2,000μmであると考えられた．また，muc（低分化）は単変量解析で有意差はみられなかったが，特異度が高く，重要な危険因子であると考えられた．この結果から，危険因子をスコア化し，大腸SM癌の内視鏡的切除後の追加腸切除の適応基準を作成した．その感度は100％，特異度は72.7％で，overtreatment症例が減り，より精度の高い選別が可能となると考えられた．

　There are currently no universally accepted indications and criteria for additional colorectal resection after endoscopic resection of submucosally invasive cancer. The purpose of the present study was to establish accurate indications and criteria for such additional resection based on the risk of lymph node metastasis. We investigated 182 submucosally invasive colorectal cancers and analyzed the pathologic risk factors for lymph node metastasis. The tumors were evaluated for pathologic factors in the area of invasion, and factors were compared between the cases with lymph node metastasis（17 cases, 9％）and those without. Univariate logistic regression analysis showed depth of invasion, cribriform type structural atypia, absence of lymphoid infiltration, lymphatic permeation, and venous permeation to be statistically significant as risk factors for lymph node metastasis. Multivariate logistic regression analysis showed the important risk factors to be, in decreasing order, lymphatic permeation, absence of lymphoid infiltration, cribriform type structural atypia, venous permeation, and depth of invasion. Submucosal invasion of 2mm or more was shown to be a risk factor for lymph node metastasis. Pathologic criteria（scoring system）based on our findings enables more accurate identification of patients who should undergo further surgical treatment after endoscopic resection.