Health Information and Tools > Patient Care Handouts >  Sentinel Node Biopsy for Breast Cancer: Before Your Procedure

Main Content

Sentinel Node Biopsy for Breast Cancer: Before Your Procedure

What is a sentinel node biopsy for breast cancer?

A sentinel node biopsy is a type of procedure. It checks to see if breast cancer has spread to certain lymph nodes in your armpit. These are called sentinel lymph nodes.

First the doctor injects a blue dye or a radioactive material into your breast. You may get both. These flow through the lymph system to help the doctor find the correct lymph nodes. Then the doctor makes a small cut to remove your sentinel lymph nodes. Sometimes the doctor removes other lymph nodes too, if it looks like the cancer has spread. The cut is called an incision. It leaves a scar that usually fades with time. The dye leaves a blue mark on your breast. It will fade in a few weeks.

If the test shows that your cancer has spread to your lymph nodes, you and your doctor will discuss what you can do. Your doctor may remove more lymph nodes. Or you may decide to use chemotherapy or radiation.

You will probably go home the same day. Most people can go back to work and their usual routine in 2 to 7 days.

This type of biopsy often is done at the same time as other breast surgeries. If this is the case, you will get information about those too.

How do you prepare for the procedure?

Procedures can be stressful. This information will help you understand what you can expect. And it will help you safely prepare for your procedure.

Preparing for the procedure

  • Be sure you have someone to take you home. Anesthesia and pain medicine will make it unsafe for you to drive or get home on your own.
  • Understand exactly what procedure is planned, along with the risks, benefits, and other options.
  • Tell your doctor ALL the medicines and natural health products you take. Some may increase the risk of problems during your procedure. Your doctor will tell you if you should stop taking any of them before the procedure and how soon to do it.
  • If you take a medicine that prevents blood clots, your doctor may tell you to stop taking it before your procedure. Or your doctor may tell you to keep taking it. (These medicines include aspirin and other blood thinners.) Make sure that you understand exactly what your doctor wants you to do.
  • Make sure your doctor and the hospital have a copy of your advance care plan. If you don't have one, you may want to prepare one. It lets others know your health care wishes. It's a good thing to have before any type of surgery or procedure.

What happens on the day of the procedure?

  • If a radioactive tracer is used, you will need to get it injected into your breast late in the day before the procedure or early in the day of the procedure. If blue dye is used, it will be injected into the breast during the procedure.
  • Follow the instructions exactly about when to stop eating and drinking, or your procedure may be cancelled. If your doctor has instructed you to take your medicines on the day of the procedure, please do so using only a sip of water.
  • Take a bath or shower before you come in for your procedure. Do not apply lotions, perfumes, deodorants, or nail polish.
  • Do NOT shave the surgical site yourself.
  • Remove all jewellery, piercings, and contact lenses.
  • Leave your valuables at home.

At the hospital or surgery centre

  • Bring a picture ID.
  • Before surgery you will be asked to repeat your full name, what surgery you are having, and what part of your body is being operated on. The area for surgery may be marked.
  • A small tube (IV) will be placed in a vein, to give you fluids and medicine to help you relax. Because of the combination of medicines given to keep you comfortable, you may not remember much about the operating room.
  • You will be kept comfortable and safe by your anesthesia provider. The anesthesia may range from making you fully asleep, to simply numbing the area being worked on. This will depend on the procedure you are having, as well as a discussion between your doctor, the anesthesia provider, and you.
  • As you wake up in the recovery room, the nurse will check to be sure you are stable and comfortable. It is important for you to tell your doctor and nurse how you feel and ask questions about any concerns you may have.

When should you call your doctor?

  • You have questions or concerns.
  • You don't understand how to prepare for your procedure.
  • You become ill before the procedure (such as fever, flu, or a cold).
  • You need to reschedule or have changed your mind about having the procedure.

Where can you learn more?

Go to

Enter U700 in the search box to learn more about "Sentinel Node Biopsy for Breast Cancer: Before Your Procedure".

Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.