Clinicopathological Outcomes of Microsatellite Instability in Colorectal Cancer

According to Global Cancer Statistics, higher than 1.9 million new cases of colorectal cancer (CRC) and 935,000 deaths are estimated to occur in 2020, representing about one in 10 cancer cases and deaths. Overall, it ranks third in colorectal incidence but second in mortality.

In CRC evolution, the acquisition of genomic instability is a critical point, and there are at least two different pathways in the pathogenesis of CRC: the chromosomal instability (CIN) pathway (85%) and the microsatellite instability (MSI) pathway (15%).

Microsatellite instability (MSI) is a phenotype that occurs due to a malfunction in the DNA repair mechanism and is seen in approximately 15% of colorectal cancers (CRCs). CRCs with MSI have different clinical features, such as a tendency to settle in the proximal colon, poor differentiation, and more lymphocytic infiltration in the tumor. It has been shown that CRCs with MSI have a better prognosis and respond differently to chemotherapy than CRCs with microsatellite stable (MSS).

We aimed to evaluate the different histopathological features of tumors with MSI compared to MSS in patients who underwent surgery for colorectal cancer. We also planned to determine how MSI affects prognostic parameters such as mortality rate, recurrence, disease-free survival, cancer-specific survival, and overall survival.