The purpose of this study is to determine whether measuring the fluid in your arms using Bioimpedance Spectroscopy is as effective at detecting and monitoring lymphedema as measurements with the Perometer. The investigators will also evaluate any symptoms you may experience in your arms during and after treatment for breast cancer with a questionnaire.

During the study whenever you have an arm volume measurement using the Perometer, we will also measure the fluid in your arms using Bioimpedance Spectroscopy. These measurements are made by passing a harmless electrical signal of very low strength through your body to determine the difference in the amount of fluid in each arm. The test is simple and painless, and takes about 3 minutes. In addition, whenever you have an arm measurement, you will be asked to complete a questionnaire. While completing the questionnaire, you can skip any questions you do not wish to answer. The questionnaires will take about 10 minutes to complete. Arm measurements with the Perometer and Bioimpedance Spectroscopy and completion of the questionnaire will occur every 4-7 months when you are at MGH for regular medical visits.

Inclusion Criteria:

• Histologically or cytologically confirmed invasive or in-situ carcinoma of the breast
• Participants must have undergone sentinel node mapping or axillary dissection
• Life expectancy of greater than 1 year.
• Willingness to comply with required follow up Perometer and BIS measurements and completion of LEFT-BC questionnaire

Exclusion Criteria:

• Patients who have known metastatic disease or other locally advanced disease in the thoracic or cervical regions
• Any patient who will not be returning routinely for follow-up at MGH or DFHCC
• Participants with known brain metastases will be excluded from this clinical trial because of their poor prognosis and because they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events
• History of primary lymphedema
• History of prior surgery or radiation to the head, neck, upper limb, or trunk
• Participants who have evidence that axillary lymph node malignancy is causing lymphedema due to recurrence as per physician discretion
• Any patient who has bilateral lymph node mapping or dissection
• Any patient with a current case of cellulitis
• Patients with a history of a different malignancy are ineligible except for the following circumstances. Individuals with a history of other malignancies are eligible if they have been disease-free for at least 5 years and are deemed by the investigator to be at low risk for recurrence of that malignancy. Individuals with the following cancers are eligible if diagnosed and treated within the past 5 years: cervical cancer in situ, and basal cell or squamous cell carcinoma of the skin

Subjects with histologically or cytologically confirmed breast cancer who will be returning routinely for follow-up at Massachusetts General Hospital

Participants included in analysis who had at least one post-operative follow up measurement

7 years