Just under your skin, above your muscles, lies your lymphatic system. It’s a series of tiny, thin tubes called vessels that carry a nutrient-rich fluid, called lymph. The vessels travel through a web of lymph nodes — small, round organs that store white blood cells and filter bacteria and waste. Lymph fluid helps your body fight infection and then drains to other parts of your body. Your lymph system also removes fluid that leaks out of blood vessels, returning it to the system that handles your heart and blood.

To stay healthy, lymph fluid must keep moving. When lymph nodes are damaged or removed because of surgery or radiation, scar tissue can form and keep fluid from draining. At first, the tissue may feel firm and thick, but as fluid backs up swelling and inflammation set in. If the swelling continues, the protein-filled fluid increases the risk for infection and more swelling.

Surgery can cut through the lymphatic channels, breaking up the pathways where lymph travels. Your risk for lymphedema after surgery depends on:

• The type of breast cancer surgery you had
• The location and number of lymph nodes removed
• The way your body drains the fluid after surgery
• The way your body heals afterward

SurgerySurgery in the armpit, or axillary, region removes lower lymph nodes where the breast and underarm tissue meet. Higher lymph nodes in the underarm area may also be removed.

• An axillary lymph node dissection removes many nodes in the lower to mid-upper underarm.
• Sentinel lymph node biopsy removes only the main nodes to which the breast lymph drains, typically one to three nodes in your lower armpit. Lymphedema can develop after sentinel node biopsy, but it happens at a lower rate than with an axillary dissection.
• If you had both breasts removed in a bilateral mastectomy, your risk is on the side or sides where lymph nodes were taken.

Radiation Therapy Radiation therapy  can also increase the risk for developing lymphedema:

• It can cause scarring, or fibrosis, that prevents lymph flow.
• The wider the area of the breast radiated and the more of the underarm the radiation reaches, the greater the lymphedema risk.
• Postmastectomy radiation, radiation to the chest wall after the breast is removed or reconstructed, can lead to lymphedema, especially if the lymph node area also is radiated.

• Having more than 10 lymph nodes removed
• Having multiple lymph nodes with cancer
• Having radiation therapy
• Getting an infection on the side of your body that had surgery
• Overuse or trauma to the hand or arm on the affected side
• Being a younger age at cancer diagnosis
• Being overweight or obese
• Gaining weight after treatment
• Certain chemotherapy treatments, such as the taxanes

Measuring the arm helps detect lymphedema. If possible, have the circumference (the distance around) of your arms measured before surgery or radiation to get a baseline reading. Some facilities take baseline measurements before treatment and measure your arms regularly afterward. If there is a change in size, you can start treatment quickly.

Some techniques used to measure the volume and size of your arm include:

• Circumference measurements use a tape measure to look for swelling in the arm. This is the most common method. Your provider will measure your arms from your hand to the armpit at different places. These places will be the same every time your arms are measured.
  • Any change in circumference of more than 2 centimeters, at any place in the affected arm, may suggest lymphedema.
• Bioimpedance passes low-dose electricity through the arm to see if you have extra fluid on the side where you had cancer. The electricity is about the same as you would get during an EKG. For this test, a provider places electrodes on each wrist and your right foot. Cables are attached to each site for a few minutes. The test does not hurt. The resistance to the electricity will be different on the affected side if you have lymphedema.
  • This test is available to people who do not have implanted metal, such as a pacemaker or defibrillator.
• Perometry passes infrared signals through your arm to measure the volume of fluid. This method uses a machine called a perometer. You will sit or stand beside it and stretch your arm over a table as a square frame passes over your arm. After measuring both arms, the perometer compares the volume of fluid in milliliters between your two arms.
  • This test is best given before lymph node surgery and every 3 months after. It is available at limited facilities and through research studies.
• Volumeter, or water displacement, is rarely used.

Some doctors use special x-rays to see lymph flow to diagnose lymphedema. Others look at the area on a CT or MRI scan.

If you already started treatment, it helps to see a lymphedema therapist to talk about your personal risk. Some facilities will monitor your arm circumference for months to years after treatment. You can also monitor your arm size using a spring-loaded (not cloth) tape measure. To keep constant pressure, measure around your arm every 4 to 10 centimeters. If the circumference has increased by more than 2 centimeters, a lymphedema therapist should check your arm. If you see any signs or symptoms of lymphedema, contact your providers as soon as possible.