A selection algorithm for internal mammary sentinel lymph node biopsy in breast cancer

Internal mammary lymph-node (IMN) metastases in breast carcinomas have a major influence on survival, comparable with the influence of axillary lymph-node metastases (ALNM). Prospective, randomized trials have demonstrated that complete IMN dissection as part of extended radical mastectomy does not improve overall or disease-free survival. In the subset of patients with tumours 1cm or less in size and no ALNM, information on IMN status would provide important information. In these cases, the presence of IMN metastases would change the staging from stage I to stage IIIB, according to the current tumour, node and metastasis classification. More importantly, it would influence these patients' adjuvant treatment. Lymphatic mapping for sentinel lymph-node (SLN) biopsy has demonstrated extra-axillary drainage in up to 35% of patients. Recent reports have demonstrated the feasibility of internal mammary sentinel lymph-node (IM-SLN) biopsy. Here we review the general prognostic and clinical significance of tumor location and lymph-node metastases in breast cancer and discuss the specific factors associated with IMN identification, metastases and treatment in the pre-SLN and SLN eras. Based on our review, we propose an algorithm for a selective approach to IM-SLN in breast cancer.