To analyze breast cancer patients with intramammary sentinel lymph node, we reviewed T1-T2N0 breast cancer patients who underwent sentinel lymph node mapping using radioisotope methods. Intramammary sentinel lymph (ISN) nodes were detected in 4 of 166 patients. Three of four ISNs were present in completely different quadrants of the breast from those of primary lesions. Although two patients had no involved nodes, including ISNs, the remaining two with T2 tumor had metastasis of ISNs alone with resulting upstaging. We should keep in mind the presence of intramammary SN in regions apart from the primary tumor, particularly when performing breast conservative surgery.