大腸ポリペクトミー後の局所再発病変の特徴

Morphological Features of Local Recurrent Adenomas and Carcinomas of the Colon and Rectum after Polypectomy

要旨　最近の10年間に国立がんセンターで大腸ポリペクトミー後，局所再発を来した10症例11病変を対象に，再発病変の肉眼的・組織学的特徴について検討した．対象症例の初回ポリペクトミー時の組織学的所見は腺腫4病変，腺腫内癌5病変，sm癌2病変であった．腺腫と腺腫内癌症例のポリペクトミー前と再発時の肉眼形態的推移をみると，ポリペクトミー前Ⅰp型の5病変は再発時にはⅠp型2例，Ⅰs型，Ⅱa型と結節集籏型の各1例へと変化していた．その他のポリペクトミー前Ⅰs型の2例はⅠs型とⅡa型の各1例に，Ⅱa型の1例はⅡa型に，結節集籏型の1例は小結節に変化し，再発病変では背が低くなる傾向が認められた．また，9病変中4病変にひだの集中や潰瘍搬痕像を認め，ポリペクトミー後の再発像の特徴と考えられた．組織学的変化をみると，初回ポリペクトミー時に腺腫であった4病変は腺腫2病変，腺腫内癌2病変に推移し，腺腫内癌5病変は腺腫4病変，腺腫内癌1病変へと変化していたが，sm癌や進行癌などの浸潤癌に変化したものは認められなかった．sm癌2症例ではポリペクトミー後の経過観察中，2例とも粘膜面に異常所見を認めない時期が存在した後，6か月後と7か月後に進行癌像として認められた．また，1例ではポリペクトミー部位近傍にリンパ節転移が粘膜下腫瘍像として認められた．

　We analyzed 10 local recurrent cases (11 lesions) of colorectal adenomas and/or carcinomas after polypectomy in our hospital during the last decade, and studied their macroscopic and histological features. Their histological findings at the initial polypectomy were adenomas; four lesions, cancers in adenoma; five lesions, and submucosal cancers; two lesions.

　As for macroscopical difference between the initial lesion and the recurrent one in the cases of adenoma and cancer in adenoma, three out of five type Ⅰp lesions were recognized as type Ⅰs, type Ⅱa and nodule-aggregating appearance at recurrence, and one type Ⅰs lesion as type Ⅱa, one nodule-aggregating lesion as a nodule. Accordingly, recurrent lesions were supposed to have a tendency to become short compared with their initial height before polypectomy. Also, converging folds and ulcer scars were considered to be characteristic as they were found in four out of the nine lesions.

　Histologically, two out of the four adenomas changed to cancers in adenoma, and four out of the five cancers in adenoma became adenomas at recurrence. Those which changed to submucosal invasive cancers and advanced cancers were not found among the nine lesions.

　In the two polypectomized cases of submucosal cancers, advanced cancers were found at the same site as the initial lesion on the six-month and seven-month follow-up examination. Endoscopically and radiographically, no abnormal finding was recognized on the mucosal surface until then. And in one case, lymph node metastasis adjacent to the polypectomy site was seen as a submucosal tumor.