We reviewed the literature regarding internal mammary lymph node metastasis in the management of breast cancer. Internal mammary dissection or radiotherapy provides no survival advantage in breast cancer patients. However, internal mammary nodal metastasis is an important independent prognostic factor. Patients with such metastases are candidates for systemic adjuvant hormonal therapy and/or chemotherapy. Moreover, in patients with histologically confirmed internal mammary metastases, irradiation of the nodes is appropriate for local control. Noninvasive techniques, such as internal mammary lymphoscintigraphy, parasternal sonography, computed tomography, and magnetic resonance imaging, are not satisfactory for the practical diagnosis of internal mammary metastasis. At present, biopsy of the internal mammary nodes in the first and second intercostal spaces is indicated for assessing nodal status and planning treatment.