胃癌の診断にX線検査は不要か―必須としない立場から：特に微小胃癌の内視鏡診断能に関して

Evaluation of the Endoscopic Features of Minute Gastric Cancer

要旨　内視鏡で発見された微小胃癌46例につき，通常内視鏡所見を中心に検討した．Ⅱa型微小胃癌は，ほぼ周囲の粘膜と同じ色調を呈するもの，表面が発赤して，過形成性ポリープと類似した病変，周囲粘膜より褪色した腺腫に類似した所見を呈する病変がみられた．Ⅱa型微小胃癌は腺腫様形態を呈する症例が多く，Ⅱb型微小胃癌では，印環細胞癌は“褪色斑”として，高分化型腺癌例は“色むらのある発赤斑”として認識された．Ⅱc型微小胃癌は表層型のうち質的診断が困難であり，その内視鏡所見は“隆起に偏在するびらん”，“星芒状発赤”，“色むらのある発赤”として認識された．比較的，陥凹が粘膜の深部にまで及んでいる症例では，悪性所見が認められる症例が多かった．微小胃癌の診断には，粘膜の微細な変化を読み取ることが肝要であると考える．

　The aim of this study was to determine the endoscopic features of minute gastric cancers (less than 5 mm in diameter) in order to facilitate its early and exact diagnosis.

　A total of 46 minute gastric cancers were included in the study. According to their appearance, eight cases corresponded to Ⅱa type cancers, three cases to Ⅱb type and the remaining 35 cases were Ⅱc type cancers. Most Ⅱa type lesions endoscopically showed adenoma-like appearance. Five lesions had discolored surface compared to the surrounding mucosa, one of them presented redness but in two lesions no change in color was evident. Among the three Ⅱb cancers, two of them corresponded pathologically to signet-ring cell carcinomas, endoscopically showing discoloration; the third case was a well-differentiated adenocarcinoma presenting uneven redness on endoscopic observation. Considering these data, for the detection of Ⅱb type lesions attention should be paid to slight mucosal color changes. Although the morphology of Ⅱc type lesions was variable, both their detection and correct diagnosis turned out to be relatively easy. Nevertheless, those lesions measuring 3～4 mm did not show malignant signs endoscopically, and were initially diagnosed as benign erosions. When the depression was less than half of the thickness of the mucosa (m₁), no malignant signs were evident, whereas lesions whose depressions were deeper than half of the thickness of the mucosal layer (m₂) showed findings suggestive of malignancy. Most of the cases which were difficult to diagnose were seen as erosions, star-like redness or uneven redness.