10mm未満の大腸癌―その肉眼的な特徴と深達度判定法

Morphological Study on Colonic Carcinomas Smaller than 10 mm with a Special Reference to Their Depth of Invasion

要旨　外科切除大腸にみられた10mm未満の大腸癌23例を対象として，その肉眼的特徴および肉眼的深達度判定法を検討した．m癌は18/23（78.3％），sm癌は5/23（21.7％）であった．早期癌全体からみた10mm未満の癌の深達度別発生頻度はm癌で18/70（25.1％），sm癌で5/47（10.6％）であった．10mm未満の大腸癌は決してまれなものではなく，sm癌も存在するので，小さな病変であってもsm癌の可能性を念頭に置く必要がある．肉眼型をみるとm癌には広基性が比較的多く10/18（55.6％），sm癌ではⅡa＋Ⅱc型と有茎性とが各々2/5（40％）ずつを占めた．一般に大腸sm癌の肉眼的判定法には胃癌のそれが適用でき，（1）無構造な表面性状―癌のsm浸潤を示す所見―sm癌37/47（78.7％），（2）病変周囲粘膜の押し上げ像と外反像―癌がsmに塊状に存在する所見―癌がsmに塊状に存在する病変の23/28（82.1％），（3）表面陥凹の存在―従来sm癌の肉眼的指標とされる―sm癌26/47（55.3％）が挙げられた．しかし有茎性の病変は一般に癌のsm浸潤量が少ないため，上記所見を欠くことが多かった．10mm未満の癌のsm浸潤判定法は一般の大腸sm癌のそれと同じで，10mm未満の癌5例のうち4例が上記のいずれかの肉眼所見を示した．いずれの肉眼所見も示さなかった1例は有茎性の病変であった．

　Twenty-three small carcinomas of the colon surgically resected were examined macroscopically and histologically to assess the macroscopic characteristics and the depth of their invasion. The materials, all smaller than 10 mm in size included 18 intramucosal carcinomas and 5 invasive carcinomas (sm). The incidence of intramucosal carcinomas smaller than 10 mm in size was 18/70 (25.1％), and that of submucosal carcinoma 5/47 (10.6％). Thus, the incidence of small invasive carcinoma is not so rare, much attention should be paid to small lesions to detect invasive carcinomas. Macroscopically, 10 (55.6％) out of 18 intramucosal carcinomas were sessile lesions, while most of the invasive carcinomas were either Ⅱa＋Ⅱc type or pedunculated lesions (2/5 each).

　We assessed the depth and amount of submucosal invasion of early colonic carcinoma according to the criteria for gastric carcinoma. The results were as follows:

　1) Amorphous surface appearance was regarded as the evidence of invasive carcinoma.

　2) Evertion of marginal non-neoplastic mucosa indicated massive submucosal invasion of carcinoma.

　3) Depression was seen in the cases with submucosal invasion.

　The sensitivity of these three findings was 78.8％, 82.8％, and 55.3％, respectively. Pedunculated submucosal carcinomas eluded these criteria because of the minute amount of submucosal invasion.

　Finally, at least one of these three findings were seen in 4 out of 5 cases of small submucosal carcinomas smaller than 10 mm in size.