早期胃癌における生検診断過程の実態

Real Effects of Endoscopic Biopsy for Early Gastric Cancer

　生検診断能を客観的に評価することは極めて難しい．なぜならば，生検採取された標本に癌が証明されなければ，その病変は癌と診断されないことが多いからである．そこで生検診断を云々する場合には，勢い診断された側からの評価，つまり癌と診断された症例を中心とした一方的な評価になってしまい，真の生検診断能をみるという立場からすると，いかにも不十分な感をまぬがれないのである．今回，著者らはこの点を十分考慮しながら，早期胃癌における生検診断過程の実態を，まず病巣の形態別に胃内各部位における一般的な生検診断成績から分析し，次に，生検診断が特に重要となるⅡb型（以下Ⅱb）や微小胃癌の診断の現状をみることで，この実態に少しでも迫ってみようと思う．

　胃生検診断の問題点

　生検組織片を採取する行為において，何よりも基本となるものは，生検部位targetの認識であろう．言い換えれば，1つの粘膜変化を見付けてその変化に対して狙撃生検をしようとする行動ができるかどうかである．これは内視鏡器種および生検装置の性能を語る以前の問題であろう．より多くの早期胃癌，とりわけⅡbやⅢ型，微小癌（≦5mm）といったものを発見するためには，この基本認識が特に重要であることは論を待たない．だから内視鏡検査に従事する医師は，常にこれをより高度のレベルで維持することが何よりも大切である．そのうえで，生検診断そのものが現在当面している個々の問題点を考察する必要がある．

　It is very difficult to evaluate the result of biopsy for early gastric cancer because in many cases, the diagnosis of the lesion is made from the study of the biopsy specimens. Thus, the real effects of endoscopic biopsy was sought by examining the biopsy results in various parts of the stomach after dividing early gastric cancer into the elevated and depressed types. Subsequently, the effects were also studied in those of Ⅱb type and microcancer.

　The diagnostic rate of the elevated type (109 lesions) was 95.4%, and each rate on the lesser curvature of the antrum, the posterior wall and greater curvature of the corpus was poor. Moreover, the biopsy results from the lesion less than 2 cm in diameter was also poorer. In the depressed type (257 lesions), it was 94.9%, and each rate on the lesser curvature of the antrum and corpus was worse. But, the size of the depressed lesions did not affect the result of biopsy.

　In the diagnosis of Ⅱb type of the early cancer and microcancer (≦5 mm in diameter), the role of endoscopic biopsy must be especially important. Thus, the diagnostic process was analyzed. Seventeen (29.3%) of 58 lesions of Ⅱb have been diagnosed only with biopsy. Endoscopic findings were mainly classifted into two: red and white discolorations of the gastric mucosa. In order to detect more lesions of Ⅱb, it is more important that these two findings are carefully observed and accurate biopsy must be performed.

　Forty-nine lesions of microcancer have been detected in our institute, but only 25 lesions (51.0%) of them were diagnosed with gastric biopsy. And, a special feature of the biopsy from the microcancer showed, statistically, the importance of the first specimen in the several specimens obtained.

　These showed that further improvement of the fiberscope, development and application of a more helpful method for easy biopsy such as dye endoscopy, and training of competent endoscopists are essentially vital.