Axillary sentinel node (A-SN) biopsy is a standard procedure in breast cancer surgery. Sampling of intenal mammary sentinel nodes (IM-SN) is not performed routinly, although it is also considered an important prognostic factor of breast cancer. The role of this latter procedure was investigated in cases of IM-SN visualized on lymphoscintigraphy. Between January 2001 and June 2012 1542 patients with clinically node negative operable primary breast cancer had sentinel node biopsy (SNB). Both axillary and IM-SN were sampled (whenever detected), based on lymphoscintigraphy, intraoperative gamma probe detection and blu dye mapping. Lymphoscintigraphy showed IM-SN in 83 cases. IM-SN biopsy (IM-SNB) was succesfull in 77 patients (93%). A total of 86 IM-SNs were removed. IM-SN involvement was identified in 14 cases, representing 18% of patients who underwent IM-SNB. This included macrometastases (MAC) in 5 cases, micrometastases (MIC) in 2 cases, isolated tumor cells (ITC) in 7 cases. No significant differences were found between patients with and without IM-SN involvement in terms of age, tumor location, tumor size, axillary involvement, tumor grade or estrogen receptor status. The IM-SN involvement has lead to new therapeutic indications in 2 cases (2.6%), both of them due to MAC in the IM-SN: in 1 case change in chemotherapy and in 1 case change in radiotherapy, with the addition of iradiation of the internal mammary chain. Based on this series and information from the literature, we conclude that the indication for an IM-SNB procedure is very limited and its routine use should not be recommended.