大腸腺腫の形態と分布―腺腫と癌について

Macroscopic Feature and Anatomic Distribution of Colorectal Adenoma

要旨　大腸癌との関連性で問題となる腺腫の特徴を1.5cm以下の病変で大きさ・占拠部位・肉眼形態から求めた．1.5cm以下では大きくなるにつれて腺腫の割合が増した．小さな腺腫では腫瘤型が多く，大きくなるにつれて長茎型が増えた．平盤型は大きさに関係なく一定であった．長茎型の腺腫は小さい病変ほど深部大腸に多い．腫瘤型の腺腫は占拠部位と大きさに一定の傾向がなかった．平盤型の腺腫は大きさに関係なく深部大腸の割合は一定であった．小さな大腸癌で腺腫の有無をみると，長茎型・腫瘤型は腺腫との関連性が高くみられ，平盤型・中央陥凹型はこの関連性が乏しかった．

　Colorectal lesions (2,554 lesions; 1,808 adenomas, 68 cancers) smaller than 3.1 cm in diameter, either polypectomized or surgically resected, were analyzed macroscopically and histologically.

　The smaller a polypoid lesion was, the less likely that the lesion was adenoma especially in the rectum and sigmoid colon. Polypoid lesions of 0.6 cm to 1.5 cm in diameter were macroscopically classified into four types (type-a: lesions with long stalk, type-b: sessile or subpedunculated lesions, type-c: plaque-like lesions, type-d: lesions with central depression) . Among the lesions of 0.6 cm to 0.9 cm in diameter type-a adenoma was most frequently seen in the right side colon. Type-b adenoma had no predilection for a specific anatomic distribution. About 30 of type-c adenoma were found in the proximal to descending colon. Type-d lesions were all malignant. Type-a and -b of colorectal early cancer smaller than 1.6 cm in diameter had positive relationship with the presence of adenoma, while type-c and -d had no such relationship.