Microsatellite Instability (MSI)

What is Microsatellite Instability (MSI) analysis test?

Microsatellite Instability (MSI) analysis detects Microsatellite Instability (MSI) in tumor DNA using PCR molecular techniques. MSI is caused by defects in the mismatch repair (MMR) system, leading to errors in repetitive DNA sequences called microsatellites. The test classifies tumors into either MSI-High (MSI-H) – significant instability or MSI-Low (MSI-L) or Microsatellite Stable (MSS) – minimal or no instability.

Why consider Microsatellite Instability (MSI) analysis test?

• To identify patients who may benefit from immunotherapy (e.g., PD-1/PD-L1 inhibitors)
• To screen for Lynch syndrome (hereditary cancer risk)
• To guide treatment planning and prognosis in cancers like Colorectal cancer, Endometrial cancer, Gastric cancer
• MSI-H status often indicates better prognosis and distinct treatment response

Who should get this MICROSATELLITE STABILITY INDEX (MSI ANALYSIS) test?

• Patients diagnosed with colorectal, endometrial, gastric, or other Lynch-associated cancers
• Individuals with family history of Lynch syndrome or early-onset cancers
• Patients being considered for immune checkpoint inhibitor therapy
• All newly diagnosed colorectal cancers (as per NCCN and international guidelines)

More Information

OTHER NAMES: MSI Testing by PCR, Microsatellite Instability Test, MSI Analysis for Lynch Syndrome Screening, Tumor DNA Instability Test, Molecular MSI Profiling

Microsatellite Instability (MSI) is a condition of genetic hypermutability resulting from a defective DNA mismatch repair (MMR) system. When the MMR system is impaired, errors that normally occur during DNA replication—especially in short repetitive DNA sequences called microsatellites—are not corrected, leading to instability. Cancers commonly associated with MSI: Colorectal cancer, Endometrial (uterine) cancer, Gastric cancer, Ovarian cancer, Small intestine cancer