What is a sentinel lymph node injection?

A sentinel lymph node injection is used to identify the main (sentinel) lymph gland in the underarm. Glands (also known as lymph nodes) act as the defence system against infection or disease. 

The sentinel lymph node injection is carried out before your sentinel lymph node biopsy which will take place either later the same day or the following day.  

The injection helps identify the nodes that your surgeon may want to perform a biopsy on. 

A tiny amount of radioactivity will be injected into your breast by a radiographer or a nuclear medicine technologist. This may sting momentarily but any discomfort usually disappears quite quickly. You will be in the department for approximately 20 minutes.

What are the benefits?

The benefit of this procedure is that it can help your surgeon find lymph nodes that may not be easily seen. 

You will also receive an injection of a blue dye to help show these glands but that is done during your operation. 

Radiation is a form of energy which occurs widely in nature and can also be human-made. We are all exposed to naturally-occurring sources of radiation in our day to day lives, such as radioactivity in buildings, rocks and soil or cosmic radiation during a plane trip. 

In Nuclear Medicine we use human-made radioactivity to help in the diagnosis of illness. 

The injected radioactivity will disappear from your body quite rapidly.

Will I receive much radiation?

No, the amount of radiation you receive is small, similar to that of some x-ray examinations and typically similar to what you would receive from natural background radiation over one or two months. 

The expected benefits of the injection outweigh any possible radiation risks.

The radiographers and technologists in Nuclear Medicine are highly trained to keep your radiation dose to the minimum necessary. 

There are no special preparations for the injection.

You can eat and drink as normal.  

For this procedure you may carry on taking your usual, regular tablets and medicines. 

You may bring a companion with you but waiting space is limited. 

Please do not bring children or anyone who may be pregnant with you. 

Although the radiation risk to others is very small, to reduce unnecessary exposure to radiation, we ask that you avoid close contact with children and anyone who may be pregnant for the rest of the day. This is because the cells of babies and young children are more sensitive than adult cells to radioactivity. Close contact means having a small child sitting on your lap or next to you for more than half an hour.  

If you think you may be pregnant or you are breastfeeding, please contact us in advance as it may be necessary to delay your appointment or give you some other special instructions. 

  • Following your injection, you can go home or return to work 
  • For the first 24 hours after your injection try to avoid prolonged close contact with babies, small children and anyone who is pregnant 
  • You are safe to drive home following the injection
  • We will provide you with some paperwork which you should take with you on the day of your surgery

To ensure that your visit to our department is as pleasant as possible, please feel free to ask the radiographer or technologist any questions you may have before, during or after the scan. 

You can contact us on: 

Call 0151 556 5052

If appropriate, for general information you can contact the Cancer Information and Support Services Team: 

Please also note that the information in this leaflet applies to Nuclear Medicine sentinel lymph node injections carried out in the Radiology Department at The Clatterbridge Cancer Centre.

If you have tests performed elsewhere or receive treatment (therapy) with radioactive materials, you should receive separate information relevant to those procedures.

Issue Date: March 2023
Issue Number: 4.2
Reference: LDIZHSLNI
Review date: March 2025