Abstract Introduction: Although previous randomized controlled trials have suggested that axillary surgery may be omitted in patients with clinically node-negative breast cancer with tumor ≤ 2cm (pT1), approximately 15% of these patients were found to have lymph node (LN) metastasis. Furthermore, while these studies demonstrated that axillary surgery, including sentinel LN biopsy, does not provide a therapeutic benefit, concern remain regarding the prognostic impact of occult LN metastasis. Therefore, the aim of our study was to identify factors associated with LN metastasis in small tumors (≤ 2cm) and to analyzed its impact on recurrence. Methods: We identified patients with pT1 primary breast cancer who underwent treatment at two hospitals between September 2003 and December 2019. To ensure accurate assessment of pathologic LN metastasis, patients who received neoadjuvant systemic therapy or did not undergo axillary surgery were excluded. Multivariate analysis was performed to identify factors associated with LN metastasis and to evaluate the impact of LN metastasis on recurrence-free survival (RFS). Results: A total of 1,745 patients were included in the study, of whom 384 (22.0%) had axillary LN metastasis. In the multivariate binary logistic regression model, LN metastasis was significantly more common in tumors larger than 1cm (odds ratio OR, 2.94; 95% confidence intervals CI, 0.15-4.08; P0.001) and in the presence of lympho-vascular invasion (OR, 4.41; 95% CI, 3.37-5.78; P0.001) while it was less frequent in tumors with histology other than ductal or lobular type (OR, 0.45; 95% CI, 0.22-0.89; P=0.022). In the multivariate Cox proportional hazard model, LN metastasis was identified as a significant risk factor related with worse RFS (hazard ratio, 1.99; 95% CI, 1.26-3.14; P=0.003). In subgroup analysis, LN metastasis was associated with poor prognosis across most subgroups, with its impact being particularly pronounced in patients with tumors1cm, histologic grade I or II, and the HR+/HER2- subtype. Conclusion: Our study found the factors associated with a higher likelihood of LN metastasis in small (pT1) breast tumors and confirmed that LN metastasis is associated with wore prognosis. Because the presence of LN metastasis can increase the risk of recurrence, even in small tumors, careful consideration should be given to performing axillary surgery to avoid potential undertreatment in patients with a high risk of LN metastasis. Citation Format: J. Lee, K. Yeonjoo, P. Youri, L. Young Ah, W. Joo Hyun, L. Woo Sung, K. Hee-Joon, M. Byung-In. Factors associated with lymph node metastasis and its prognostic impact in breast cancer patients with small tumors (≤2cm) abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-11-02.
Lee et al. (Tue,) studied this question.