Absence of Microsatellite Instability In Soft Tissue Sarcomas

Objective: Here, we analyze a series of soft tissue sarcomas (STS), which are a heterogeneous group of mesenchymal neoplasms, for the presence and frequency of microsatellite instability (MSI). MSI has been proposed to be clinically relevant for colorectal cancer, yet on STS its role is not consensual, partly due to the limited number of cases analyzed and methodology issues. Methods: The detailed evaluation of MSI in tumor samples from 71 STS patients was performed by pentaplex PCR of the MSI markers NR-27, NR-21, NR-24, BAT-25, and BAT-26, followed by capillary electrophoresis. The expression of DNA mismatch repair (MMR) proteins (MLH1, MSH2, MSH6, and PMS2) was also evaluated in suspected MSI-positive cases by immunohistochemistry. Results: The MSI analysis showed instability of one MSI marker in a total of 3 cases (4.2%). However, MMR protein expression was not affected, demonstrating that all cases were microsatellite stable. Conclusion: Our results suggest that MSI does not play a role in STS tumorigenesis.