This double-blind, randomized, controlled clinical trial comparing patient-reported pain and pain medication/narcotic use between patients randomized to treatment (bupivacaine) or placebo (saline) delivered via pain pump to the mastectomy site. Candidates will have chosen to have a mastectomy on one side immediately followed with tissue expander placement breast reconstruction.

Patients will be randomized 1:1 to bupivacaine- (treatment) or saline-(placebo) filled percutaneously-placed pain pumps; neither the participants nor the study staff will know participants' treatment. Data on patient-perceived pain and pain medication use will be collected before surgery, during surgery, and after surgery on Days 1, 2, 3, 7, and 90, and at Years 2 and 4 by phone.

The investigators hypothesize that patients randomized to the treatment (bupivacaine) group will have significantly lower pain scores and use less pain medicine than patients who receive placebo during the first 90 days following their surgery. The Year 2 and Year 4 follow-ups are included as tertiary endpoints to capture differences in chronic pain, and patients will be asked to complete the same questionnaires as at the Day 90 follow up.

Double-blind, randomized, controlled clinical trial comparing patient-reported pain and pain medication/narcotic use between patients randomized to treatment (bupivacaine) or placebo (saline) delivered via pain pump to the mastectomy site. Candidates will have elected to undergo unilateral post-mastectomy immediate tissue expander breast reconstruction. Participants meeting inclusion criteria will be enrolled and baseline data collection completed prior to randomization and surgery.

Patients will be randomized 1:1 to bupivacaine- (treatment) or saline-(placebo) filled percutaneously-placed pain pumps in a double-blinded design. Patient-specific surgical details will be recorded intraoperatively. Following the surgery, post-operative pain, pain medication/narcotic use, and assessment for adverse events (AEs)/serious adverse events (SAEs) will be assessed on Days 1, 2, and 3. A clinic visit occurs on Day 7 when the pain pump will be removed and additional data collected (updated medical history, pain medication/narcotic use, AEs/SAEs, and study questionnaires). A Pain Pump Questionnaire will be completed to obtain the patient's assessment of the usability of the pain pump.

Long-term quality-of-life/health outcomes assessments will be done on post-operative Day 90 (±14 days), Year 2 (±14 days), and Year 4 (±14 days). The Year 2 and Year 4 follow-ups are included as tertiary endpoints to capture differences in chronic pain, and patients will be asked to complete the same questionnaires as at the Day 90 follow up.

Inclusion Criteria:

• Be Female aged 18-100 years.
• Choose unilateral mastectomy followed by immediate tissue expander breast reconstruction.
• Have no inflammatory breast cancers.
• Be aware of the nature of her malignancy.
• Understand the study purpose, requirements, and risks.
• Be able and willing to give informed consent.

Exclusion Criteria:

• Any concurrent narcotic analgesic use (baseline narcotic use must be 0 to be eligible).
• Axillary lymph node dissection related to qualifying mastectomy.