Frequency of microsatellite instability in breast cancer determined by high-resolution fluorescent microsatellite analysis

In breast cancer, the rates of positivity for microsatellite instability (M SI), vary greatly in the literature. Using high-resolution fluorescent micr osatellite analysis (HFRMA), we studied microsatellite alterations in 75 pa tients with sporadic breast cancer. In this system, several devices were pr epared to improve reproducibility of polymerase chain reaction products, mi gration accuracy of electrophoresis, and characteristics of the detection s ystem. Precise and objective analyses of microsatellite alterations are mad e feasible using HRFMA. Seven of the 75 cases were judged to be positive fo r MSI, the rate of positivity being 9.3%. This rate is relatively low compa red to the data in the literature. All the microsatellite changes observed in this system can be classified into two types: type A with relatively sma ll changes in microsatellite sequences observed in limited loci and type B with drastic and widely dispersed changes. The former was thought to be con nected to abnormal activity in DNA mismatch repair (MMR). Among the 7 cases , 6 (8.0%) had type A alterations, which means that the tumors may have an abnormal MMR activity. Application of precise and objective systems for mic rosatellite analysis is expected to be clinically useful to detect patients at high risk for cancers. Copyright (C) 2000 S. Karger AG, Basel.