[Progress in evaluating the risk of lymph node metastasis in early colorectal cancer]

Early colorectal cancers refer to invasive cancers that have infiltrated into the submucosa without invading muscularis propria, and approximately 10% of these patients have lymph node metastases that cannot be detected by conventional imaging. According to the guidelines of Chinese Society of Clinical Oncology (CSCO) Colorectal Cancer, early colorectal cancer cases with risk factors for lymph node metastasis (poor tumor differentiation, lymphovascular invasion, deep submucosal invasion and high-grade tumor budding) should receive salvage radical surgical resection; however, the specificity of this risk-stratification is inadequate, making most patients undergo unnecessary surgery. Firstly, this review focuses on the definition, oncological impact importance and controversy of the above "risk factors". Then, we introduce the progress of the risk stratification system for lymph node metastasis in early colorectal cancer, including the identification of new pathological risk factors, the construction of new risk quantitative models based on pathological risk factors, artificial intelligence and machine learning technology and the discovery of novel molecular markers associated with lymph node metastasis based on gene test or liquid biopsy. Aim to enhance clinicians' understanding of the risk assessment of lymph node metastasis in early colorectal cancer; we suggest to take the patient's personal situation, tumor location, anti-cancer intention and other factors into account to make individualized treatment strategies.