潰瘍性大腸炎における癌のサーベイランスの問題点―問題例を通して

Problems in Cancer Surveillance in Ulcerative Colitis

要旨　潰瘍性大腸炎に合併するcolitic cancerのサーベイランスにおける問題点を示すため2例の症例を提示した．①40歳男性で左側大腸炎型．経過10年のサーベイランスにてgiant pseudopolypのポリペクトミーと周囲の生検を行った．この生検は異型なしと判断されたが見直し診断にて異型が疑われた．2年3か月後のサーベイランスでは腫瘍性隆起を認めdysplasia associated lesion or mass（DALM）と判断しDALMの生検でlow grade dysplasia，周囲粘膜の生検でhigh grade dysplasiaを認め大腸全摘を施行した．結果は漿膜浸潤陽性の進行癌であった．拡大内視鏡は腫瘍性隆起と炎症性ポリープの鑑別は可能であったが，深達度診断には有用でなかった．生検病理診断の問題，サーベイランス間隔の問題，深達度診断の問題などを示した．②42歳男性で左側大腸炎型．経過8年の頻回再燃型で再燃を来して当院へ紹介．当院の初回内視鏡で直腸に結節集簇型様の3cm超の病変を発見．生検で高度異型腺腫と区別できなかったが，頻回再燃でもあり大腸全摘術を施行．術後病理では活動性の潰瘍性大腸炎に合併した3.8cm×3.0cm大の結節集籏型様の腺腫内癌と判断された，本症例をcolitic cancerと考えると，左側大腸炎型に対しても7～8年目からサーベイランスを開始する必要性を示唆する．今後も問題例を集積して，サーベイランス失敗例のないように改良していくことが必要と考えられた．

　We report here two patients with rectal cancer associated with ulcerative colitis. Both cases showed some problems in cancer surveillance. Case 1 was a 40-year-old male with left-sided colitis for 12 years' duration. The result of previous surveillance was negative, but rectal cancer involving the serosal surface was found after an interval of two years and three months. Problems of pathological interpretation of the biopsy specimen and the surveillance interval were discussed. Case 2 was a 42-year-old male with left-sided colitis for 8 years' duration. He had persistent symptoms and was referred to our hospital. The first colonoscopy revealed an adenoma-like tumor 3.8 cm × 3.0 cm in his rectum. Total colectomy was carried out and the tumor was, pathologically, adenocarcinoma in an adenoma, suggestive of coincidental tumor not closely associated with colitis. The relatively short duration of his colitis and the evidence of left-sided colitis were compatible with these pathological findings. New endoscopic (magnifying colonoscopy ?) and histopathologic techniques should be developed to improve the identification of the dysplastic lesion which, so far, is not easily visible with routine examination.