Histogenesis of Large Bowel Carcinoma of the Type Is (Protruded and Sessile Type) with Submucosal Invasion Yo Kato 1 , Tsuyoshi Nakayama 1 , Akio Yanagisawa 1 , Koichi Koizumi 2 , Hirotoshi Ohta 3 1Department of Pathology, Cancer Institute 2Department of Internal Medicine 3Department of Surgery, Cancer Institute Hospital Keyword: 大腸癌の成り立ち , Is型大腸sm癌 , polypoidgrowth , PG pp.1473-1478
Published Date 1997/10/25
DOI https://doi.org/10.11477/mf.1403105224
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 We considered the histogenesis of large bowel carcinoma of the type Is, i.e. protruded and sessile type, with submucosal invasion, which recently attracted much attention as an immediate precursor of advanced carcinoma, using 10 〔six endoscopically resected (ER) and four surgical〕 cases. All the tumors were 10 mm or more in size (largest diameter), and the ER cases, 10~20 mm (13 mm in average) were larger than those of the surgical cases, 20~30 mm (24 mm in average). Histologically, most of the tumors showed overt carcinomas of well differentiated or moderately differentiated type (not of very well differentiated type), and the invasion depths were sm1 (sm shallow) in three, sm2 (sm intermediate) in six and sm3 in one, the surgical cases having, in general, deeper invasion than the ER cases. Polypoid growth (PG) indicating the presence of intramucosal tumor growth twice or more as thick as the thickness of the surrounding uninvolved mucosa existed in nine of 10 cases. Adenomatous component was found in five of six ER cases, but in none of the surgical cases, which suggested that the adenomatous component was replaced by carcinoma as the size of the tumor increased. Thus, large bowel carcinoma of type Is with submucosal invasion may be formed mainly through PG tumor and adenoma, and only rarely through non-PG tumor and de novo carcinoma.

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