Although the internal mammary (IM) lymph node status is a major prognostic factor in breast cancer, IM nodal staging is not common practice. In order to improve nodal staging, we have routinely performed IM sentinel node (SN) biopsy and have adjusted adjuvant treatment accordingly. We reviewed the outcome of these patients. Data from 764 patients were available for follow-up. A total of 406 patients had no lymph node metastases (group 1), 330 patients had axillary metastases (group 2), 7 patients had IM metastases only (group 3) and 21 patients had both axillary and IM metastases (group 4). Mean follow-up was 46 months. Prognosis did not appear to be worse for patients with IM metastases compared to those with axillary metastases only, which might indicate that they benefit from improved staging and tailored adjuvant treatment algorithms. However, long-term follow-up data, preferably in larger series, are needed to support our findings.