Breast Cancer, Lymph Node Biopsy, and Dissection

If you’ve been diagnosed with breast cancer, doctors will need to know if the cancer has spread beyond your breast. To find this out, they’ll remove one or more of your lymph nodes under the arm on the side where the cancer was found.

This is called lymph node biopsy and dissection. The procedure has two main purposes.

  1. It allows the surgeon to figure out what stage the cancer is in by learning how far it has spread.
  2. It removes the breast cancer that may have spread into the lymph nodes in the armpit.

There are two ways for doctors to remove and test lymph nodes:

Sentinel node biopsy. The surgeon injects a special blue dye, a radioactive substance, or both into your breast in the area of the tumor. That helps them determine which lymph nodes are the first to receive drainage from the breast -- these nodes would potentially be the first to be invaded by cancer cells. One to three sentinel nodes are usually removed and tested for cancer. If the results are negative, the cancer hasn’t spread to the lymph nodes.

Axillary node dissection. At least six of the lymph nodes under your arm are removed and sent to a lab to be checked for cancer. This method is a very reliable way to check the extent of your cancer. But it can take a while to recover, and it can have complications like lymphedema (swelling of the arm) or nerve damage.

If you have an axillary node dissection, a drain will be placed under your arm to remove fluids that may build up and cause swelling. The wound is then closed.

After the procedure, you’ll likely need to stay in the hospital 1 to 2 nights. If you had reconstructive surgery at the same time, your stay may be longer. You may go home with the drain in place. Your doctor will remove it a few days later.

It’s common to have some swelling. You can take pain medication as needed. Most of the healing is done in about 6 weeks.


A physical therapist can teach you simple exercises to relieve muscle soreness and tightness. Your surgeon may suggest more intense exercises after the stitches are out.

Before you have surgery, get a good understanding of what’s going to happen and what you might expect. Print out these Questions to Ask.

Make sure your doctor gives you:

  • Specific instructions to follow in the days before surgery
  • An overview of the surgical procedure
  • Information about recovery and follow-up care

After surgery, watch for warning signs of an infection or swelling in your arm or hand. Call your doctor immediately if you see a buildup of fluid, redness, or other symptoms of infection.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on November 17, 2019



The Mayo Clinic: "Sentinel Lymph Node Biopsy."

National Cancer Institute: “Sentinel Lymph Node Biopsy.”

Breast “Axillary Lymph Node Dissection” and “Sentinel Lymph Node Dissection.”

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