表面型大腸腫瘍内視鏡診断の問題点

An Issue Concerning Endoscopic Diagnosis of Superficial(TypeⅡ) Colorectal Epithelial Neoplasm

要旨　表面型大腸腫瘍85病変（癌52，腺腫33）の内視鏡（拡大内視鏡も含む）所見を中心に，その肉眼型分類と質的診断に関する問題点を検討した．癌ではⅡcが最も多く，腺腫ではⅡcとⅡaが同数であった．Ⅱcはその大半（約70％）が，陥凹周囲に反応性過形成粘膜の隆起を伴っていた（Ⅱc＋ME）．これら病変の内視鏡と組織ルーペ像での形態分類は両者間で少なからず乖離を認めた．病変が微小なほど検査時の空気量や伸展固定の影響を受けやすい．したがって乖離も生じやすく，その場合は無理に分類せず単に表面型微小癌（腺腫）としておけばよいと考えられた．拡大内視鏡観察では，反応性過形成粘膜は大型円形ピット，腺腫では大型管状ピット，癌では小型類円形ピットや無構造所見を多く認めた．

　The macroscopic classification (Fig. 1) and the qualitative diagnosis of superficial colorectal epithelial neoplasms (typeⅡ) were evaluated in 85 cases (52 cases of carcinoma, 33 cases of adenoma). Most type Ⅱ colorectal carcinomas were of the superficial depressed type (Ⅱc). On the contrary, typeⅡ colorectal adenoma showed both type Ⅱc and type Ⅱa (flat elevated) in equal incidence. Most (70%) type Ⅱc lesions showed marginal elevation surrounding the depression (type Ⅱc+ME). This marginal elevation consisted of reactive hyperplastic glands.

　There were some discrepancies between endoscopic and microscopic classification of the lesions (Fig. 4). The smaller the lesion, the more easily the shape was affected by pneumatic distention at endoscopy and by stretching at fixation (Fig. 3). Thus, the discrepancies between macroscopic and microscopic findings were common in the case of minute lesions. It was thought to be unnecessary to classify minute lesions by subtype. It would be sufficient to describe them as type Ⅱ carcinoma or type Ⅱ adenoma.

　Magnifying endoscopic pictures showed mucosa with reactive hyperplastic glands with a large, regular round pit-pattern, revealed adenoma to have an irregular big tubular pit-pattern, and identified cancer as having irregular big loss of pit-pattern (Fig. 9).