STAGING OF GASTRIC CANCER INVASION BY ENDOSCOPIC ULTRASONOGRAPHY

Abstract

One hundred and six patients with gastric cancer (49 cases of early cancer, and 57 cases of advanced cancer) were examined by endoscopic ultrasonography (EUS) to determine the depth of the cancer invasion. In normal cases, the gastric wall appeared as a five-layered structure. In cancer patients, however, this structure exhibited thickening, defect, and interruption. These features were measured and employed as the EUS criteria for the classification of cancer invasion. According to this classification, cancer invasion was divided into mucosal, submucosal, proper muscular, and subserosal-serosal types. EUS diagnostic accuracy rate of early cancer was 79.6% (39/49 cases). The accuracy rate for ulcerated lesions was low (76.2%) as compared to non-ulcerated ones (100%). The causes of EUS misdiagnosis of the lesion were fibrosis (7 cases), incomplete detection (2 cases), and microinvasion of the submucosal layer (1 case). However, the wsm/wm ratio (the width of irregularities in the 3rd layer/the width of irregularities in the 1st and 2nd layer) which increased in proportion to the extent of fibrosis, proved useful in reducing the EUS misdiagnosis due to fibrosis. Although solitary cases of fibrosis and microinvasion of the submucosal layer were misinterpreted by EUS, when they existed simultaneously, the diagnosis was paradoxically correct, because fibrosis was misinterpreted by EUS as the invasion of the submucosal layer and histologic cancer invasion was at the same depth due to the microinvasion. The EUS diagnostic accuracy rate of advanced cancer was 93.0% (53/57 cases). The width of irregularities in the 4th layer by EUS (wpm) in advanced cancer increased in proportion to the depth of the lesions, and proved useful in specifying the depth of invasion into the subserosa (ssα-ssγ) and serosa. The diagnostic accuracy rate of the prognostic serosal factor (ps) was as high as 89.5% (51/57 cases), when the ps was determined as follows: wpm>40mm=ps(+) (as deep as ssγ or deeper); wpm<40mm=ps(-) (as deep as ssβ or not as deep).