MICROSATELLITE INSTABILITY - MSI ANALYSIS

Unstable microsatellites may occur as a result of mutations in MMR genes. These DNA sequences, which cannot be matched as a result of replication, repeat and accumulate, creating genomic instability. High MSI also increases the frequency of mutations in cancer-related genes.

Thanks to some molecular markers, MSI measurements can be made from tumor tissue. It is defined in three main groups according to the measurement results: no unstable marker detected: MSI-stable (MSS); Less than 30% instability: low MSI (MSL); More than 30% instability: high MSI (MSH).

In some cancers (especially colon), MSI status is very important prognostically. Additionally, treatment options may vary depending on whether the MSI is high or low in the chemotherapeutic plan to be used in cancer.

While MSI status can be examined by immunohistochemical methods, the accepted “gold standard” in diagnosis is molecular genetic methods.

• STR (SHORT TANDEM REPEAT) Analysis