A patient with a history of breast cancer underwent 3-phase (99m)Tc-methylene diphosphonate (MDP) imaging followed 3 d later by 3-phase (99m)Tc-sestamibi (MIBI) imaging. During the vascular and blood-pool phases, a lymph node over the right clavicle was seen on both the (99m)Tc-MIBI and the (99m)Tc-MDP scans at as early as 30 s and then became hotter. Four months after receiving chemotherapy, the patient achieved a complete response. The lymph node over the right clavicle vanished on ultrasound examination. The similar distribution of the blood-pool phase between the (99m)Tc-MDP and (99m)Tc-MIBI scans indicated that (99m)Tc-MIBI may similarly provide information on vascularization of the lymph node. In addition to indicating vascularization, our (99m)Tc-MIBI protocol may simultaneously provide information on P-glycoprotein expression important for predicting chemotherapy sensitivity. With information on the resistance of a tumor to drugs and the environment in which it dwells, chemotherapy sensitivity might be predicted more precisely.