Swollen Lymph Nodes – COVID Vaccine Reaction or Breast Cancer?

As an OB/GYN, I frequently order mammograms (3-D) for my patients. Recently, I’ve seen a few reports showing increased lymph node enlargement on one side of the breast tissue. Although this may send an alarming signal of possible breast cancer, it may very well be linked to a recent CO-VID vaccination administered in that same arm and NOT be due to breast cancer.

Why does the swelling occur?

Let me explain and give you an example to help clarify. A patient, who is right-handed, gets her first CO-VID vaccination in her left arm, the non-dominant arm. Within a few days, her lymph nodes in her left underarm, also known as axillary region, begin to swell. This is a NORMAL bodily response to a vaccine as the body mounts an immune response to the vaccination, as the usual drainage system flows to this lymphatic tissue in the underarm.

Given that the CO-VID vaccines thus far, Moderna and Pfizer, are made using mRNA technology, a relatively newer method for vaccine production, radiologists have seen a more robust swelling in the lymph nodes than seen previously with yearly flu vaccinations. As we learn more and more about the side effects of these vaccines as well as the virus itself, we can collect more data regarding side effects within various individuals.  


What are some more alarming causes of lymph node swelling?

As with any new finding on examination, it is important that you provide a detailed history to your doctor as well as undergo a thorough examination. Swollen lymph nodes underneath the armpit can also be a sign of BREAST CANCER, as the natural drainage of lymphatic tissue inside the breast tissue flows into this area.

Swollen lymph nodes in other areas of the body, including the chest, neck and groin can be due to:

  • A cold or case of the flu
  • Sinus infection
  • Strep Throat
  • Mononucleosis
  • Lymphoma
  • Autoimmune conditions: rheumatoid arthritis, lupus, etc.

 How long does the swelling in the underarm last?

Usually swelling will develop within 2-3 days after receiving the vaccine, on the same side that the vaccine was given and should subside within days to a few weeks.

Should I still get my mammogram done?

Yes! With CO-VID, many patients have delayed their mammograms and it is important to get screening done – with a 3-D mammogram for better sensitivity. Please read a previous blog post regarding how this 3-D technology literally saved my life!


Tips for timing your mammogram:

If possible, get your mammogram BEFORE your first CO-VID shot or 4-6 weeks AFTER your second shot.

If you have a mammogram already scheduled, many radiology centers are flexible in their scheduling to accommodate for patients receiving the vaccine. Please make sure to tell the radiology technician when you received the vaccine and in which arm it was placed.

Believe me – it will save YOU, the radiologist and your GYN – a lot of possible stress!

In health and happiness,

Dr. Diana

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