We reported a 24-year-old female patient with the history of ectopic axillary breast cancer which was removed surgically. Sentinel node mapping was performed for lymphatic axillary staging of this patient with two injections of the 99m-Tc-phytate in both ends of the surgical scar. Lymphoscintigraphy showed an axillary sentinel node which was harvested during surgery and was not pathologically involved. Our case showed that sentinel node mapping is possible for ectopic axillary breast cancer patients even after excisional biopsy of the index lesion.