Congo red-methylene blue testで診断しえた典型Ⅱb型早期胃癌の1例

Early Gastric Cancer of Absolute IIb Type Diagnosed by the Endoscopic Congo Red-Methylene Blue Test, Report of a Case

はじめに

表面平坦型早期胃癌Ⅱbは従来組織学的に初めて診断されるような微小癌が主体を占め，Ⅱb=微小胃癌と考えられてきたが，谷口は微小癌としての点状Ⅱb以外に，数cmに及ぶ拡がりを持った面状Ⅱbが存在することを指摘している．内視鏡的には点状Ⅱbでは存在診断そのものが問題となり，面状Ⅱbではその拡がりを正確に診断することが問題となる．

　内視鏡的には類似Ⅱb，1cm以上のⅡb，単発Ⅱbでは術前に"癌"と診断可能なものが多いが，典型Ⅱb，1cm以下のⅡb，副病変としてのⅡbの内視鏡診断成績は著しく不良である，特に典型Ⅱbでは内視鏡的には，粘膜の褪色，アレア像の異常，低凹凸，異常発赤，易出血など慎重に撮影し読影しなければ見逃されてしまうような軽微な所見を呈し，背景胃粘膜としての胃炎性変化との鑑別が困難なものが多く，また病変存在部が撮影されているにもかかわらず，何らの異常所見も指摘できないものも少なくない．

　Although a large variety of diagnostic methods and tools are available, a correct diagnosis of early gastric cancer of type IIb was very difficult. By routine endoscopic examinations, a correct diagnosis was possible only in 20% of the absolute IIb lesions. But endoscopic Congo red-methylene blue test developed in our hospital raised rate to correctly diagnose IIb lesions. By this test, cancer lesions could be observed as areas where both Congo red and methylene blue became white. In the present report, we demonstrated a case of early gastric cancer of absolute IIb type, which was correctly diagnosed by the endoscopic Congo red-methylene blue test. Routine endoscopic examination revealed a slightly elevated lesion on the greater curvature of the antrum (Figs. 1 and 2). After application of methylene blue followed by Congo red, irregular areas where both dyes were bleached emerged in the whole antrum (Fig. 3).

　Biopsy specimens revealed a well-differentiated tubular adenocarcinoma. The cancer lesion could not be identified with the naked eye in the specimens obtained by gastrectomy (Fig. 4), whereas histological examinations confirmed a wide-spread early gastric cancer. Histologically, cancer cells of well-differentiated type were found to be confined within the mucosal layer and there was no niveau difference between the cancer lesion and the non-cancerous mucosa (Figs. 5 and 6). Therefore, Congo red-methylene blue test was very useful for the diagnosis of early gastric cancer of type IIb.