Clinicopathological features and risk stratification for lymph node metastasis in early-stage colorectal cancer (from intramucosal carcinoma to SM2): a large-scale retrospective study based on a Chinese population

To analyze clinicopathological features and lymph node metastasis (LNM) risk factors in early-stage colorectal cancer (CRC, ranging from intramucosal carcinoma to SM2) in Chinese patients, with a focus on stratifying SM2 tumors into low- and high- risk groups based on cumulative pathological factors, and to optimize treatment strategies for SM1/SM2 subgroups. A retrospective study included 1693 patients with early-stage CRC (2010-2019) from Zhongshan Hospital, Fudan University. Clinical data, treatment methods, and histopathology were analyzed, with prognostic follow-up (median 44 months). Overall, the probabilities of LNM from intramucosal carcinoma to SM2 stage are 0.9%, 2.6%, 4.5%, and 15.6%. SM2 depth (P = 0.027), lymphovascular invasion (LVI) (P < 0.001), and high-grade histological classification (P = 0.043) were independent LNM predictors. LNM rates increased with cumulative adverse indicators (0-4 indicators: 4.4%、11.8%、17.0%、27.1%、30.3%; P < 0.001). In the SM2 subgroup, high-grade histology and LVI were independent risk factors. Notably, SM2 patients with ≥ 2 risk factors (high-grade histology / LVI / intermediate and high-grade tumor budding) had significantly higher LNM rates (20.5%-33.3%) (P < 0.05), whereas SM1 tumors could not be further stratified. Thus, the key finding is that SM2 tumors can be meaningfully stratified into low- and high- risk groups for LNM based on cumulative pathological indicators. This exploratory study provides a risk stratification framework for LNM in early-stage CRC, demonstrating that SM2, but not SM1, tumors can be stratified into low- and high-risk subgroups using cumulative pathological features. External validation is needed before clinical application.