Background: Accurate assessment of the internal mammary (IM) nodal basin can impact prognosis and treatment in breast cancer. The goal of this study was to identify characteristics associated with positive IM sentinel lymph nodes (SLNs) and the impact on adjuvant treatment.
Methods: Clinically node-negative breast cancer patients who underwent SLN dissection including removal of IM SLNs were identified and medical records were reviewed. Statistical analysis was performed using Fisher's exact test and rank-sum tests with a significance level of 0.05.
Results: IM SLNs were removed in 71 patients, 60 (85 %) had negative IM SLNs, whereas 11 (15 %) had positive IM SLNs. Clinicopathologic characteristics were similar between the groups. The majority of patients in both groups had axillary SLNs removed (95 % in the node-negative group vs. 91 % in the node-positive group). Four patients (36 %) with positive IM SLNs had axillary metastasis; thus, IM nodal metastases were the only nodal metastases in 64 % of patients with positive IM SLNs. The identification of IM metastases altered adjuvant therapy in 5 (45 %) patients with positive IM SLNs.
Conclusions: Patients with positive IM SLNs have clinicopathologic features similar to those of patients with negative IM SLNs limiting the ability to predict IM nodal metastasis preoperatively. The identification of IM nodal metastases significantly impacts treatment decisions, especially when IM nodes are the only site of nodal metastasis. Removal of IM SLNs should be considered when lymphoscintigraphy reveals IM drainage.