大腸の異時性多発癌におけるⅡc型大腸病変

A Study of Depressed Type Colorectal Cancers in Metachronous Multiple Cancers

要旨　1985年4月から1999年2月までの期間に当センターおよび関連施設にて切除された異時性多発癌62症例，164病変を対象とし，隆起型（Ip，Isp，Is），表面隆起型（Ⅱa，Ⅱa＋dep），LST（laterally spreading tumor），陥凹型（Ⅱc，Ⅱc＋Ⅱa，Ⅱa＋Ⅱc，Is＋Ⅱc），進行癌に分けて検討した．対象症例中の陥凹型の割合は25.8％と極めて高く，第2癌以降の浸潤癌における陥凹型の割合も29.4％と極めて高かった．陥凹型の異時性多発は25％と高頻度に見られた．第1癌が進行癌であるものを除いて第2癌以降に進行癌がみられたものは，陥凹型群では0，非陥凹型群では3病変認められた．したがって進行癌の予防を目的として検査，摘除を行う以上，隆起型癌ばかりでなく陥凹型癌の存在を十分に念頭におく必要があると思われた．

　We studied metachronous multiple cancers to reveal the importance of depressed type cancer in the development of colorectal cancer. We defined metachronous multiple cancers as lesions in which we detected more than two cancers over a period of one year. During the period from April, 1985 to February, 1999, we encountered 15,759 colorectal tumors (1,300 early cancers, 767 advanced cancers) which were treated either endoscopically or surgically. We selected 62 patients (164 lesions) as metachronous multiple cancers. Then, we divided these lesions into five types, protruded type, flat type, laterally spreading type, depressed type and advanced cancer. The ratio of the existence of depressed type in these patients was 25.8%. This ratio was very high. For example, the ratio of the existence of depressed type among all colorectal cancers which we encountered was 7.6%, while the ratio of the existence of depressed type among early colorectal cancers which we encountered was 12.1%. The ratio of depressed cancers among second cancers was as high as 29.4%. Depressed type cancers occur at a rate of 25.0% among metachronous cancers. This also is a very high rate. Apart from cases when the first cancer is an advanced cancer, among second cancer that have become advanced none of them were the depressed type, but three of them were the non-depressed type. Therefore, we think that, if the purpose of colonoscopy and endoscopic resection is the prevention of advanced cancer, we must endeavour to detect depressed type early colorectal cancer among other types.