Sentinel Lymph Node Mapping Post-Injection Site Pain

This is a pain survey study that will compare the level of discomfort experienced by breast cancer patients after injection of either technetium-labeled sulfur colloid or technetium-labeled tilmanocept, both FDA-approved agents used for sentinel lymph node biopsy (SLNB). Breast cancer patients who are already scheduled for SLNB as part of their original surgical plan will be asked to participate in this study and be randomized to receive either technetium-labeled sulfur colloid or technetium-labeled tilmanocept. After injection, patients will complete pain questionnaires to measure the amount of discomfort they are feeling during and after they receive the injection. There will be no change to the patient's treatment plan other than the addition of pain questionnaires. The investigators' hypothesis is that patients will feel less discomfort after injection of tilmanocept versus sulfur colloid.