Different Types of Microsatellite Instability in Colorectal Adenomas
CHENG Lei 1) , WANG Hui ping 2) , HUANG Qiong 1) , LAI Mao de 1)* ( 1) Department of Pathology, School of Medicine, Zhejiang University, Hangzhou 310006, China; 2) Department of Pathology, First Affiliated Hospital of Zhejiang University, Hangzhou 310006, China)
The MSI status of 16 microsatellite loci of 62 adenoma specimens from 59 patients were detected by means of manual microdissection PCR SSLP. The overall MSI rate of the 16 microsatellite loci was 14 4%, and the frequency of MSI H (microsatellite instability high frequency) was 9 7%. Both adenoma and carcinoma cells were obtained from 10 patients. The MSI status of adenoma and carcinoma at certain loci may be different; and at certain loci carcinoma showed faster shifting bands than adenoma, which meant a shorter microsatellite sequence in carcinoma; There were no significant differences of MSI H with respect to age and sex of patients, or the site and histological subtypes of the adenomas. MSI H patients were younger than MSI L patients (56 50��11 38 vs. 60 36��11 34) and more common in female (5/6) MSI H group was not tubular adenoma histologically; MSI alteration rates at these loci of TGF��R��(A) 10 , hMSH6, TCF4, BAT26 in MSI H group were significantly higher than those in MSI low group ( P <0 05, and P <0 01 as to BAT26). It could be concluded that microsatellite instability existed even in the early stage of colorectal tumorigenesis. MSI could be dynamically changing with the progression of the colorectal tumors, and certain microsatellite alterations might occur only at certain stage of colorectal carcinogenesis. The difference between MSI H and MSI L groups existing in carcinoma is also seen in adenomas. MSI H and MSI L adenomas may be two types of colorectal adenomas.