As a normal side effect to most vaccines, the axillary lymph nodes in the arm pit area on the side where vaccination took place can temporarily swell up or become enlarged — a sign that the vaccine is working by mounting an immune response. This is called unilateral axillary lymphadenopathy (UAL).
While the reaction is not uncommon, higher rates of UAL than normal are being reported following the COVID-19 vaccines, and mistaken for a potential symptom of breast cancer.
“The rate of enlargement is more common compared with the other vaccinations,” said Dr. Sandeep Ghai, division head of breast imaging at the University Health Network, Sinai Health and Women’s College Hospital.
“Naturally there is panic and fear among women,” she added.
Enlarged lymph nodes when seen on a mammogram are also a sign of leukemia and lymphoma.
The lymph nodes become tender and swell up within two to four days after the COVID-19 vaccination, and the swelling can last for up to six to eight weeks.
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“There’s definitely more of a reaction of the immune system to this type of vaccine than some of the other vaccines that our bodies have seen before, so I think that’s one explanation for why the lymph nodes are so noticeable after this vaccine,” Dr. Lisa Mullen, assistant professor of radiology at Johns Hopkins Medicine, said.
Some women can the feel lump, but for others, the swelling is only being detected during a mammogram exam, which involves an X-ray image of the breasts.
It’s a trend radiologists in Canada and across the border in the United States are starting to see more and more of as vaccines continue to roll out.
“Every week we are seeing one to two patients either on routine mammograms or someone who sees the lump and they are coming,” Ghai told Global News.
At the Ottawa Hospital, Dr. Jean Seely, head of the breast imaging section, says she has seen at least four such cases of women with enlarged lymph nodes who came in for a breast exam after receiving a COVID-19 vaccine.
“It’s not something alarming, but it’s something that we need people to be aware of because it can be mistaken for breast cancer if we don’t have that history of the vaccination.”
As a protocol to avoid confusion, women who do come for a breast exam are being asked if they had recently received their COVID-19 vaccine.
“If there’s a history of the vaccination within six weeks of the mammogram or the swelling of the armpit, what we are recommending is that we have women be examined by their doctors to make sure that that swelling goes away within six weeks,” Seely, who is also the president of the Canadian Society of Breast Imaging, said.
But if the clinical symptoms persist for more than six weeks after vaccination, an axillary ultrasound is recommended for further evaluation.
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Similar but different
In U.S., about 11 per cent of people — in the 18 to 64 year age bracket who received the Moderna vaccine experienced swollen lymph nodes after the first dose, and 16 per cent after the second shot, according to the Centers for Disease Control and Prevention (CDC). Such cases were also reported for the Pfizer-BioNTech vaccine.
Dr. Connie Lehman, director of breast imaging at the Massachusetts General Hospital in Boston, dismissed any fears about a correlation between the COVID-19 vaccines and breast cancer.
“The vaccinations are not causing breast cancer. They’re not causing cancer in the lymph nodes.”
Despite the similarities in the symptoms, Lehman said a clear distinction can be easily made between the two.
“The signs of breast cancer are so different than the signs of unilateral swollen lymph nodes after a COVID vaccine, so that’s not a diagnostic dilemma and it’s one we feel we can manage very well,” she said.
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Breast cancers are presented as calcifications (calcium deposits), distortions and masses in the breast, whereas swollen lymph nodes post-vaccination are in the arm pit area only, Lehman explained.
Mullen said the breast tissue itself is not changing in response to the vaccine.
“The pathologist will actually see breast cancer cells in the lymph node, so we can differentiate in those few patients where it is crucial to differentiate,” she told Global News.
“But we don’t want to recommend biopsies for normal lymph nodes that are just larger because they’re processing the vaccine.”
To avoid confusion, the Canadian Society of Breast Imaging and Canadian Association of Radiologists recommend where possible, to consider scheduling screening exams prior to the first dose or six weeks after either dose in average-risk patients.
“Women who are overdue for screening due to pandemic delays or are symptomatic should proceed to mammography irrespective of the timing of the vaccination dose,” the updated guidelines from March say.
In a statement to Global News, Health Canada said: “We encourage women to discuss mammogram appointments with their health care practitioners, who will be best to advise them in light of their medical history.”
Meanwhile, the Society of Breast Imaging in the U.S. suggest a four to six week wait for the breast screening after the second dose.
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The CDC has approved the COVID-19 injection in the thigh, so that is one option for women to consider in the U.S.
If women have a personal history of breast cancer or are undergoing breast cancer treatment, Collen advised to get their vaccination on the opposite side of their body.
In any case, breast imaging experts and radiologists are not in favour of women delaying a COVID-19 vaccine or putting off their mammogram appointments.
“I really think it’s very important that women get screened, but that they also get vaccinated,” said Seeley.
The other experts agreed.
“We don’t want this in any way to dissuade women from getting their vaccinations,” Lehman said.
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