treatment, depth of invasion, tumor differentiation, lymphatic invasion, vascular invasion, tumor budding, polypoid/non-polypoid growth, adenoma component, and lymph node metastasis. Pathologically diagnosis of massive invasion was judged according to Kudo's classification of the degree of submucosal invasion. Their morphology (gross appearances) were divided into protruded, flat-elevated, and depressed type. Results: The incidence of small T1 cancers was 15.5% (179/1153). 'Small' group had significantly more depressed-type lesions('Small' 46.9% vs. 'Large' 20.1%, p<0.01), significantly lower adenoma component ('Small' 29.0% vs. 'Large' 42.6%, p<0.01) and polypoid growth ('Small' 46.4% vs. 'Large' 64.9%, p<0.01) than 'Large' group. Concerning initial treatment, 'small' group was significantly more likely to undergo endoscopic treatment, whilst the lymph node metastasis rate was not significantly different between the two groups('Small' 12.4% vs. 'Large' 10.8%, pZ0.64). Conclusion: Although 'small' T1 cancers tended to be adopted to initial endoscopic treatment, nodal metastasis rate showed no differences between 'small' and 'large'. In addition, 'small' T1 cancers contain more depressed-typed tumors. It is therefore important to take more careful assessment even when we find a 'small' lesion. And we have to do endoscopy so as not to miss any 'small' lesions.
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