A Multicenter Retrospective Analysis on Lymph Node Metastasis in Clinically Node-Negative (cN0) Patients with Small-Sized Breast Cancer.

Purpose: Sentinel lymph node biopsy (SLNB) is the standard for early breast cancer, but its necessity in small tumors with clinically node-negative (cN0) status remains debated. This study evaluated the incidence of lymph node metastasis in cN0 patients to explore the feasibility of omitting axillary surgery. Methods: A cohort of 579 women with unilateral small breast cancer and cN0 were enrolled from three hospitals in Jiangsu Province (March 2023-June 2024). Clinical nodal status was determined by ultrasonography, while pathology and immunohistochemistry assessed tumor size, node status, and molecular subtypes. Chi-square tests and logistic regression were used for analysis. Results: Lymph node metastasis was detected in 79 patients (13.64%). Tumors ≤20 mm and Ki-67 ≤14% showed significantly lower metastasis rates (P < 0.0001 and P = 0.013, respectively). Even in cN0 patients with both favorable factors, 6.15% still had nodal involvement. Logistic regression identified tumor size (T2) as an independent predictor of metastasis. Conclusion: Small breast cancer with cN0 and low Ki-67 expression is associated with reduced but non-negligible nodal metastasis. These findings support caution in omitting axillary surgery and highlight the need for individualized risk stratification rather than universal omission.