| [ Summary ] |
In 2,535 surgically resected advanced colorectal carcinomas, 33 tumors (1.3%) were thought to have originated from "LST over 30mm" (LST-advs.). LST-advs. were more frequently thought to be mp-cancer and were located less in the left-sided of the colon and more in the lower rectum, compared to non-LST-advs. The macroscopic appearance of remnant intramucosal neoplastic components in LST-advs. were "nodular-aggreaged" (21/33,64%), villous (8/33,24%), lobular (2/33,6%), and undermined (2/33,6%). Residual adenomatous components were seen in 27/33 (82%) tumors and 20/27 (74%) contained villous/tubulovillous histology. Compared with other advanced carcinomas, the incidence of tumors with carcinoma with low-grade atypia were predominant in the invasive area (8/33,24%), and tumors with mucinous component (7/33,21%) were significantly higher in LST-advs.. The invasive area within LST-advs. was located centrally in 23/33 (70%) and at the periphery in 10/33 (30%) In all tumors, accompanying adenomatous components, carcinoma was surrounded by adenomatous intramucosal histological component of adenoma, low-grade carcinoma, and high-grade carcinoma. Intramucosal components continuously adjacent to the invasive area were considered to be high-grade carcinoma in 25/33 (76%), These data indicate that 1.3% of advanced colorectal carcinoma could be considered to originate in LST over 30mm in size, especially from the LST-G subtype. However, tumors the would been originated from the LST-NG subtype may not be selected in this study and the incidence of 1.3% would be a minimal estimation for advanced carcinoma, originating from LST. LST-advs. was thought to develop through a sequential progression from adenoma to low-grade carcinoma, high-grade carcinoma, and invasive carcinoma, and it was thought to play an important role in the development of mucinous carcinoma. |