Swollen Lymph Nodes: Cancer or Covid-19 Vaccine Reaction?

Enlarged nodes in an armpit may be a side effect of Covid-19 vaccination

Photo: Sanja Radin/Getty

For those of us with breast tissue, the discovery of a lump in an armpit tends to immediately raise the specter of cancer. These lumps often occur at lymph nodes, which are debris traps for lymph fluid draining from the breast and all of the things lymph carries with it. Sometimes, cancer cells are among those things.

But the nodes also are a throughway for lymph draining from other parts of the thorax and the arm. It’s the arm that’s involved in the latest twist of the ongoing pandemic: enlarged armpit nodes after receiving one of the vaccines against Covid-19.

Clinicians are reporting a bump in the numbers of just-vaccinated patients who are concerned about swollen nodes. The top takeaway in a paper just published in The Journal of the American College of Radiology is, “prepare to see large volumes” of these swollen nodes in patients who have recently been vaccinated.

Swollen nodes are not unusual with vaccination. In fact, both Pfizer and Moderna mention them as reported side effects after administration of their vaccines. The swelling usually becomes noticeable within a few days of the jab, typically on the same side as the shot, where the nodes are dealing with draining inflammatory detritus.

Still, a swollen node can be alarming. One of our children experienced several enlarged nodes, including under the collar bone, which can be a worrying red flag for cancer. After a biopsy and a lot of blood tests, the specialists determined that his first dose of the HPV vaccine series was the likely reason for the enlarged nodes, which has been reported before. To keep things from getting too heavy for our son, who was 12 at the time, we named the largest node “Alfred.” A couple of years later, Alfred is still with us and now about the size of a pea.

A node lingering that long seems to be unusual. According to a Cleveland Clinic breast cancer specialist, with enlarged armpit nodes after a Covid-19 vaccine, the swelling should subside within a few weeks.

That’s not to say that every swollen node following a Covid-19 vaccination is associated with it. Coincidences are possible. Consulting a clinician remains the first step if you make such a discovery. In addition to vaccination or cancer cells from any region these nodes drain, other possible causes include “cat scratch disease” or the effects of silicone particles escaping from breast implants and causing inflammation.



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Emily Willingham

Emily Willingham


Journalist, author, Texan, biologist. I write All About Us (we=us), All About Adolescence (our longest growth stage), & All About Aging (we’re all doing it).