MECHANISMS PRODUCING COLOR-CHANGE IN FLAT EARLY GASTRIC CANCERS

Background and Study Aims: Although highly refined endoscopes have mad e it possible to detect not only early. gastric cancers with morpholog ical changes, but also flat-type tumors (type IIb) on the basis of the color changes observed in them, the factors responsible for color cha nges in type IIb carcinomas have not been fully elucidated, The aim of this study was to analyze the potential mechanisms underlying these c olor changes. Patients and Methods: Thirteen type IIb cancers were sel ected from a total of 589 resected gastric cancers detected preoperati vely using endoscopic examination. All of the tumors showed color chan ges alone, without surface changes, and the color changes included red ness, discoloration, and spotty bleeding, Detailed histological examin ation of the resected stomachs revealed twelve more IIb lesions that h ad not been identified at endoscopy. The endoscopic appearance of the IIb cancers were correlated with the degree of tumor differentiation, the extent of wall infiltration, and the number of capillaries. Result s: In cases that were detectable by endoscopy. the endoscopic color ap pearance correlated significantly with both tumor size (P< 0.02) and w ith the extent of mucosal cancer infiltration (P<0.02), Histological e xamination of the IIb lesions revealed that redness and discoloration were significantly more frequent in the differentiated and undifferent iated cancer types, respectively (P< 0.01). There was a significant di fference in the number of capillaries between type IIb carcinoma and t he adjacent normal mucosa, but not between cancers, The numbers for di fferences in redness and discoloration were 7.0 +/- 5.6 and -14.0 +/- 8.8, respectively. Conclusions: These results suggest that the main fa ctor underlying color change in type Ilb earl gastric cancers ma) be t he number of capillaries in the lesions, in comparison with the adjace nt mucosa, whether the lesion is visible on endoscopy, however, depend s more on its size than on the number of capillaries.