Optimizing lymph node evaluation in colorectal mucinous adenocarcinoma: a multicenter and population-based study

Background: While the currently recommended minimum number of examined lymph nodes (ELNs) for colorectal cancer is 12, the applicability of this standard to colorectal mucinous adenocarcinoma (MAC), a distinct tumor entity with high metastatic potential, remains controversial. This study aimed to establish and validate the optimal ELN threshold during surgery to achieve superior survival outcomes of MAC patients. Methods: Data from 21 Chinese medical institutions and the Surveillance, Epidemiology, and End Results (SEER) database were analyzed using Cox proportional hazards models to identify prognostic factors affecting MAC patient outcomes. Restricted cubic spline (RCS) analysis was subsequently applied to determine the optimal ELN threshold. Results: The ELN distribution pattern demonstrated significant concordance between the Chinese cohort ( n = 1086) and the SEER cohort ( n = 12 343), with identical median values (17) and overlapping interquartile ranges (SEER: 12–23 vs. China: 13–22). Multivariate analyses adjusted for potential confounders established ELN quantity as an independent prognostic factor (SEER cohort: hazard ratio [HR] = 0.987, 95% confidence interval [CI]: 0.985–0.990, P < 0.001; Chinese cohort: HR = 0.975, 95% CI: 0.957–0.994, P = 0.011). The RCS models in both databases revealed a nonlinear L-shaped association between the ELN count and all-cause mortality risk, with 17 ELNs identified as the optimal threshold. Notably, patients with ≥17 ELNs exhibited significantly reduced mortality risks in both the SEER cohort ( P < 0.001) and the Chinese cohort ( P = 0.45), particularly in node-negative patients and those without adjuvant chemotherapy. Conclusion: Elevated ELN counts are correlated with improved survival. Our findings strongly suggest that 17 ELNs is the optimal cutoff for evaluating surgical quality and prognostic stratification in MAC patients, challenging the conventional 12-ELN standard.