29 July 2021

Mammogram ‘diagnostic confusion’ following covid vax

Breast cancer Clinical COVID-19

Women having a mammogram should tell their clinician if they’ve been recently vaccinated against covid-19, because of a rare side effect that can lead to a false positive.

In some cases, mRNA covid vaccines can cause the lymph nodes to swell, which can appear on a mammogram as a potential breast cancer, Cancer Australia has warned. 

The effect was reported in association with the Pfizer and Moderna covid vaccines in the US but is yet to be reported following the Astra Zeneca covid vaccine. 

“There have been some reports internationally about people who have received a covid-19 vaccine having lymph node swelling which is being mistaken for possible breast cancer,” Cancer Australia said.

Swollen lymph glands in the underarm (lymphadenopathy) can be caused by an infection or a vaccine, but they are also a symptom of breast cancer.

“This may lead to a false positive mammogram result; that is, that the mammogram may look abnormal even though there is no cancer actually present,” Cancer Australia said in an FAQ document for patients released today.

“The Royal Australian and New Zealand College of Radiologists does not recommend delays to covid-19 vaccination nor any breast imaging (screening mammogram or diagnostic imaging for breast cancer symptoms). However, women having a mammogram should tell their healthcare professional if they have been recently vaccinated.”

People with this side effect usually present with unilateral axillary lymphadenopathy on the side of the vaccinated arm, the Royal Australian and New Zealand College of Radiologists said in a statement in June.

The symptoms usually resolve within one to two weeks, some lasting up to six weeks. 

“If lymphadenopathy persists, further investigations should be undertaken to rule out alternative conditions,” the college said. 

“The Royal Australian and New Zealand College of Radiologists notes that the rare occurrence of axillary lymphadenopathy following covid vaccinations may cause diagnostic confusion. 

“However, balanced with the risk of increased screening intervals, RANZCR does not recommend delaying screening, particularly for higher risk groups, and rural and remote populations where access to screening is not always available.”

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