The association between microsatellite instability and lymph node count in colorectal cancer

Area of Science:

• Oncology
• Pathology
• Cancer Research

Background:

• Adequate lymph node retrieval from colorectal cancer (CRC) specimens is vital for diagnosis and treatment.
• Previous research suggests tumor characteristics, including microsatellite instability (MSI), may influence lymph node counts.
• Understanding factors affecting lymph node retrieval is critical for improving CRC patient management.

Purpose of the Study:

• To investigate the relationship between MSI and lymph node retrieval in a large cohort of CRC patients.
• To determine if MSI influences the frequency of retrieving at least 12 lymph nodes and the overall lymph node count.
• To explore the impact of tumor location and stage on the association between MSI and lymph node retrieval.

Main Methods:

• Analysis of a previously MSI-typed cohort of 1196 colorectal cancer patients.
• Statistical evaluation of the association between MSI status and lymph node retrieval metrics (≥12 nodes, mean, median).
• Stratified analysis based on tumor location (proximal colon) and UICC stage.

Main Results:

• MSI was significantly associated with a higher frequency of retrieving ≥12 lymph nodes and increased mean/median lymph node counts overall.
• In proximal colon cancers, the primary site for MSI tumors, this association was not observed.
• A significant increase in lymph node count was found only in microsatellite unstable Stage I proximal colon cancers.

Conclusions:

• The previously reported link between MSI and higher lymph node counts is largely attributed to the higher prevalence of MSI in proximal colon cancers.
• MSI may be associated with earlier lymph node activation in Stage I proximal colon cancers, potentially due to tumor immunogenicity.
• These findings refine our understanding of MSI's role in colorectal cancer pathology and its impact on prognostic indicators.