Histopathologic and Macroscopic Features of Small Colorectal Carcinomas of Superficial Type (Type Ⅱ) Yasuo Ohkura 1,2 , Kyoichi Nakamura 1 1Department of Pathology, The University of Tsukuba, School of Medicine 2Department of Pathology, Tokyo Metropolitan Cancer Detection Center Keyword: 表面型大腸癌 , 微小癌 , de novo癌 , 腸管壁伸展による形態変化 , 癌組織診断基準 pp.829-836
Published Date 1990/7/25
DOI https://doi.org/10.11477/mf.1403111105
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 From the view-point of the histogenesis of colorectal carcinomas, it has been suspected that the target lesions for detecting carcinomas in the early phase are de novo carcinomas of the superficial type measuring less than 1 cm in the largest diameter. Recently, small colorectal carcinomas of the superficial type have frequently been disclosed endoscopically in Japan. Using 64 cases of small colorectal carcinomas of the superficial type less than 1 cm in the largest diameter, macroscopic and microscopic features were examined.

 Macroscopically, 46 cases were superficial elevated type (Type Ⅱa), 4 cases were superficial flat type (Type Ⅱb), 7 cases were superficial depressed type (Type Ⅱc), and 7 cases were mixed type (Type Ⅱc+Ⅱa). Most cases (72%) were Type Ⅱa carcinomas. Type Ⅱb and Ⅱc carcinomas were mostly minute ones less than 5 mm in the largest diameter. In contrast with this, most cases of Type Ⅱc+Ⅱa carcinomas were above 6 mm in the largest diameter. In invasion depth, 47 cases (73%) were intramucosal carcinomas and 17 cases (23%) were submucosal infiltrating carcinomas. The majority of submucosal infiltrating carcinomas were Type Ⅱc and Type Ⅱc+Ⅱa. By microscopic examination using the objective indices of grade of atypicalities (ING and ISA), almost all cases of small colorectal carcinomas of the superficial type were de novo without the adenomatous component. These atypicalities were much different (in structure and cellular level) from the atypicalities of small benign adenomas.

 The macroscopic appearance of small colorectal carcinomas of the superficial type changes according to the various grades of extension of the bowel wall (Figs. 7, 9, 11). To decide the macroscopic type of carcinoma of the superficial type, it is important to extend the bowel wall sufficiently. In this extended condition, Type Ⅱa carcinoma can be identified as slightly elevated lesion with flat smooth surfaces, and Type Ⅱc carcinomas appear as well-depressed lesions both macroscopically and microscopically. To distinguish these from the sessile type (Type Is), the histopathological standard of Type Ⅱa is that the height in comparison with the largest diameter is about 10%, and the height is less than 3 mm. Also, if carcinomas of Type Ⅱc+Ⅱa remain as distinctly elevated lesions when the bowel wall is fully extended, it should be suspected that they are carcinomas with massive submucosal infiltration. So it is important to discern this change of macroscopic appearance of colorectal carcinomas of the superficial type.

 To accumulate data concerning minute colorectal carcinomas of the superficial type will enable us, in the near future, to understand their histogenesis and developmental process.

Copyright © 1990, Igaku-Shoin Ltd. All rights reserved.


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