caa a22 4500 475801830 CHVBK 20180406123739.0 cr unu---uuuuu 170329e20000901xx s 000 0 eng 10.1007/s002680010149 doi (NATIONALLICENCE)springer-10.1007/s002680010149 Colorectal Carcinogenesis Based on Molecular Biology of EarlyColorectal Cancer, with Special Reference to Nonpolypoid (Superficial)Lesions [Elektronische Daten] [Toshiaki Watanabe, Tetsuichiro Muto] The multistep genetic model of colorectal carcinogenesis is based on the concept of the adenoma—carcinoma sequence. The adenoma—carcinoma sequence theory has been generally accepted for polypoid early colorectal cancers (ECCs). On the other hand, an increasing number of nonpolypoid (superficial) ECC have been reported. Nonpolypoid (superficial) ECCs show distinct characteristics histologically and genetically, and some claim these lesions may develop by de novo type carcinogenesis. In fact, clinicopathologic studies have shown that most nonpolypoid (superficial) cancers have no adenomatous lesions in the surrounding area. Genetic analyses have also revealed that nonpolypoid (superficial) ECCs show a pattern of genetic alterations different from that of polypoid ECCs. The K-ras mutation rate is lower in nonpolypoid (superficial) ECCs than in polypoid ECCs, but there is no significant difference in the p53 mutation rate between two types of tumor. During the development of ECCs, the K-ras gene seems to determine the macroscopic configuration: whether polypoid or nonpolypoid (superficial). These results suggest that nonpolypoid (superficial) ECCs originate from a pathway different from the conventional genetic pathway that follows the adenoma—carcinoma sequence. However, this does not mean that this new pathway is following de novo type carcinogenesis, because there is a possibility that nonpolypoid (superficial) adenomas, or so-called flat adenomas, develop into nonpolypoid (superficial) ECCs following the adenoma—carcinoma sequence. At the present time, there is still not enough evidence to conclude whether nonpolypoid (superficial) ECC is derived from de novo carcinogenesis or the conventional adenoma—carcinoma sequence. Further analysis, especially concerning APC gene mutation in ECCs, is essential to elucidate the carcinogenesis of nonpolypoid (superficial) ECCs. Société Internationale de Chirurgie, 2000 Watanabe Toshiaki Department of Surgical Oncology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan aut Muto Tetsuichiro Department of Surgical Oncology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan aut World Journal of Surgery Springer-Verlag 24/9(2000-09-01), 1091-1097 0364-2313 24:9<1091 2000 24 268 https://doi.org/10.1007/s002680010149 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s002680010149 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Watanabe Toshiaki Department of Surgical Oncology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan aut NATIONALLICENCE 700 1- Muto Tetsuichiro Department of Surgical Oncology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan aut NATIONALLICENCE 773 0- World Journal of Surgery Springer-Verlag 24/9(2000-09-01), 1091-1097 0364-2313 24:9<1091 2000 24 268 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer