Ⅰp・Ⅰsp型大腸sm癌の臨床病理学的特徴とリンパ節転移危険因子の解析

The Clinicopathological Features and Risk Factors of Lymph Node Metastasis of Ⅰp・Ⅰsp Type Adenocarcinoma with Submucosal Invasion

要旨　大腸sm癌249例を肉眼型よりⅠp・Ⅰsp型（48例），Ⅰs型（96例），Ⅱ型（105例）の3群に分けて，sm深達度細分類の問題点，それらの臨床病理学的特徴，リンパ節転移の危険因子について検討した．sm深達度細分類においてHaggitt分類や相対分類（sm均等3等分法）はリンパ節転移の予測には有用でなく，粘膜筋板保持群では絶対分類（sm浸潤距離測定法）により評価し，粘膜筋板消失群は粘膜筋板保持群のsm₃癌（浸潤距離1,000μm以上）と同等に扱うのが有用かつ実用的評価法と思われた．Ⅰp・Ⅰsp型sm癌は，茎を有する以外はⅠs型と悪性度など臨床病理学的にほぼ同様であり，またリンパ節転移率や転移危険因子は肉眼型により大差なく，他の肉眼型の癌と同様に取り扱ってよいと思われた．Ⅰp・Ⅰsp型sm癌のリンパ節転移危険因子は組織型（中～低分化型）と著明な間質反応のみが有意であったが，深達度，ly，簇出，著明なリンパ球浸潤の欠如も危険因子となりうることが示唆された．Ⅰp・Ⅰsp型sm癌の治療方針は，すべての粘膜筋板消失群と粘膜筋板保持群のsm₃以上（浸潤距離1,000μm以上）では外科的切除が原則で，粘膜筋板保持群のsm₁またはsm₂かつリンパ節転移の危険因子が1つもない症例は，内視鏡的切除のみで根治できる可能性が考えられた．

　We studied, pathomorphologically, 48 surgically resected colorectal carcinomas with submucosal invasion of Ⅰp・Ⅰsp type with special reference to risk factors of regional lymph node metastasis. We compared these with 96 Ⅰs type and 105 Ⅱ type carcinomas.

　With regard to the evaluation method used for the depth or level of submucosal invasion, Haggitt's classification and the relative value method were useless for estimating the risk of lymph node metastasis. In cases with preserved muscularis mucosa, the absolute value (direct measuring method of submucosal invasive depth) was useful for our purpose sm₃ carcinomas, which invaded the submucosa more than 1,000μm, had a high incidence of lymph node metastases. The absolute value method could not be used for cases in which the muscularis mucosa had vanished, but, where the muscularis mucosa was preserved, the absolute value method showed that the risk of lymph node metastasis for Ⅰp・Ⅰsp type carcinomas didn't differ from the risk involved for sm₃ carcinoma. We also found that the clinicopathological factors including risk of lymph node metastasis of Ⅰp・Ⅰsp type carcinomas were the same as those of Ⅰs and Ⅱ types. The risk factors of lymph node metastasis in Ⅰp・Ⅰsp type were histological grade (moderate to poor differentiation), prominent desmoplastic reaction, depth of invasion, lymphatic permeation, sprouting of the tumor cells, and lack of prominent lymphoid infiltration.

　In conclusion, Ⅰp・Ⅰsp type adenocarcinomas with sm₃ invasion by absolute value and unpreserved muscularis mucosa should be treated by surgical resection with lymph node dissection. In cases with sm₁ or sm₂ by absolute value, those with no risk factors can be cured by local resection alone.