文献例よりみた大腸癌の発育経過―X線画像および内視鏡画像の遡及的経過観察例の分析

Growth and Development of Colorectal Cancer―Review of Literature Describing Retrospective Follow-up by X-ray and Endoscopic Pictures

要旨　大腸癌の発育を画像で追跡した報告例を収集し，X線画像と内視鏡画像の遡及的報告例に分けて解析した．X線画像報告例は多数例を取り扱った5報告187例，内視鏡画像報告例は35症例(自験8例を含む)を取り上げた．X線画像報告例によるとその初期病変は，隆起型(Ip，Isp，Is)が多く，全体の56.9％(103/181)を占め表面陥凹型は11.6％に過ぎなかった．また，特定の速い発育を示す群を指摘できなかった．ただし，癌が早期癌にとどまる間はその発育は遅く，進行癌に至ると発育は加速された．免疫組織学的指標(p53染色指標とKi-67染色指標)は発育速度とは相関しないとされている．一方，内視鏡画像報告例は，初期病変に生検結果が加わることが特徴で，より詳細な分析が可能となる．いまだ症例数が少ない点が問題である．集計例の解析からその初期病変を推定すると，隆起型が多く(60.0％)表面陥凹型は少なく(14.3％)，X線画像報告例と全く同様な傾向が得られた．以上から，大腸癌の初期像は隆起型が多く，表面陥凹型は20％以下と推定された．極めて速い発育例は特定されなかった．臨床的には，平坦な隆起型を含め進行の速い粘膜下浸潤例を見逃さないことが重要と考えられた．

　This review aimed at collecting and analyzing reported cases of colorectal cancer with retrospective follow-up by X-ray and endoscopic pictures. In the X-ray-followed-up cases, 187 cases in five reports which dealt with a large number of cases were reviewed. In endoscopy-followed-up cases, 35 cases including our own 8 cases were reviewed.

　From the meta-analysis of the X-ray-followed-up cases, we found that the common initial feature was the polypoid type (Ip, Isp, Is) tumor which comprised 56.9％ of the total number (103/181 cases). Superficial depressed type comprised only 11.6％. Concerning growth speed, no specific type (including depressed type) was identified as showing especially rapid growth. However, many reports pointed out that mucosal cancer grew slowly and that advanced cancer showed an accelerated rapid growth. However, p53 and Ki-67 staining indices of final cancer, determined by immunohistochemical staining, had no relationship with the growth speed of tumors.

　Endoscopic retrospective study can reveal much more detail of the initial lesion including biopsy histological information. However, reported cases using endoscopy have often not been documented. In the collected 35 cases with endoscopic retrospective data the polypoid lesion was the most common initial lesion which comprised 60.0％ of the total number and the superficial depressed type lesion comprised only 14.3％. These figures are very similar to those of retrospective X-ray studies. From these results, we conclude that the most frequently found initial feature of colorectal cancer is polypoid cancer and the frequency of superficial cancer was speculated to be less than 20％. The rapidly-growing-type of cancer was not identified. Clinically, it is very important that every flat or polypoid submucosally invasive cancer, a type which grows rapidly, must be detected with certainty.