Association between MRI-based tumor-to-skin distance and axillary lymph node metastasis in breast cancer

Axillary lymph node (ALN) status is a major prognostic factor in breast cancer and influences both survival outcomes and treatment planning. Noninvasive predictors of nodal metastasis are of clinical interest. Tumor-to-skin distance (TSD) has been proposed as a potential anatomical marker; however, standardized data based on magnetic resonance imaging (MRI) remain limited.

This retrospective study included 98 female patients with pathologically confirmed breast cancer who underwent preoperative breast MRI between 2020 and 2025. Patients with prior breast or axillary surgery, distant metastasis, multifocal or multicentric disease, or inadequate MRI quality were excluded. TSD was measured on dynamic contrast-enhanced MRI by a single experienced radiologist blinded to axillary nodal status. Associations between TSD and histopathologically confirmed ALN metastasis were assessed using logistic regression analysis. Diagnostic performance was evaluated by receiver operating characteristic (ROC) analysis.

Among the 98 patients, 27 (27.6%) had pathologically confirmed ALN metastasis. The median TSD was significantly shorter in the ALN-positive group than in the ALN-negative group (10.0 mm versus 14.0 mm, p = 0.004). In multivariate analysis, TSD was independently associated with nodal metastasis (OR, 0.929; 95% CI 0.864-0.999; p = 0.048). ROC analysis demonstrated moderate discriminatory ability (AUC = 0.69). A cutoff value of 10 mm yielded a sensitivity of 62.9%, specificity of 73.2%, and a high negative predictive value of 83.9%.

A shorter TSD measured on preoperative breast MRI is independently associated with ALN metastasis. A 10-mm threshold may help identify patients at low risk of nodal involvement, supporting MRI-based TSD measurement as a complementary tool for preoperative risk stratification. Prospective multicenter studies are warranted for validation.