Clinicopathologic Features of Flat Elevations in the Colon and Their Significance

Kim, Hyun Shig; Lee, Kwang Real; Lim, Seok Won; Lee, Jong Kyun; Park, Weon Kap; Yoo, Jung Jun; Hwang, Do Yean; Kim, Kun Uk

Abstract

BACKGROUND AND AIMS
There are two main routes in the growth and development of colo-rectal carcinomas, that is to say, the adenoma-carcinoma sequence and the route described by the de novo theory. The adenoma-carcinoma sequence has been considered a principal route for colorectal carcinomas for a long time, but recently the de novo cancer theory has become a controversial issue, and many authors have claimed that their cases were de novo carcinomas. Since Muto described small "flat elevations" and emphasized their significance as precursors of colorectal carcinomas, especially of flat colorectal carci-nomas, many flat elevations have been reported. He cautioned that the reported de novo carcinomas could also be carcinomas that developed from small flat adenomas. In addition, no data are available in Korea on the subject of flat elevations. Accordingly, we attempted to analyze flat elevations in the colon and to obtain correlations between their endoscopic and histologic features and their clinical implications.
METHODS
The authors performed colonoscopic removal of 146 flat elevations from January 1997 to December 1997 at Song-Do Colorectal Hospital in Seoul, Korea. We reviewed and analyzed all those lesions. During colonoscopy, the sizes of the lesions were measured by an endoscopic ruler.
RESULTS
The most common age group was the sixth decade. Only one case involved a patient under 30 years old. The male-to-female ratio was 3.2 : 1. The numbers of flat adenomas and flat adenocarcinomas were 68 and 1, respectively. These 69 cases amounted to 47.3% of the flat elevations. The malignancy rate for flat adenomas was 1.4% (1/69). There were no malignancies in flat elevations with diameters below 10 mm. Hyperplasticpolyps and chronic nonspecific inflammation showed 34.9% and 15.8%, respectively. Most of the flat elevations were smaller than 10 mm (98.6%). Recognizable endoscopic features of the flat elevations were redness (47.3%) and depression (15.8%), but 50 cases (34.2%) of the flat elevations had no specific features. Flat elevations smaller than 5 mm had discolorations in 15 cases (14%). The sigmoid colon was the most common site of the flat elevations. The percentage of flat elevations found in the sigmoid colon and the rectum was 70.5%. Hot biopsy was the main treatment for lesions smaller than 5 mm (75.7%), and snare polypectomy was the main treament for lesions from 5 mm to 9 mm.
CONCLUSIONS
Flat elevations were detected without difficulty through careful examination. Nearly half of the flat elevations were flat adenomas. Accordingly, flat elevations may have some clinical significance on the basis of the adenoma-carcinoma sequence, but flat elevations greater than 10 mm should be managed cautiously because of possible malignancy.