What a Breast MRI Study Reveals About Axillary Lymph Nodes and COVID-19 Booster Vaccination

Vaccine-related lymphadenopathy occurs in nearly 19 percent of people who have had COVID-19 booster vaccination, regardless of age or type of vaccine, according to magnetic resonance imaging (MRI) findings from a new study.

For the 128-patient retrospective study, recently published in Academic Radiology, researchers utilized breast MRI scans taken after COVID-19 booster vaccination and breast MRI scans taken prior to initial COVID-19 vaccination to compare measurements of axillary lymph nodes ipsilateral to the side of COVID-19 booster vaccination. Seventy percent of the patients had the Pfizer-BioNTec COVID-19 booster vaccine and 30 percent of the cohort had the Moderna booster vaccine. There was a median of 31 days between COVID-19 booster vaccine administration and the post-booster vaccine breast MRI, according to the study.

The researchers found that 24 patients (19 percent) had 0.2 cm or greater increases in lymph node cortical thickness after COVID-19 booster vaccine administration. For patients with cortical thickness increases of less than 0.2 cm, the study authors noted a median of 36 days between receiving the booster vaccine and the post-booster vaccine breast MRI exam in comparison to a median of nine days for patients with 0.2 cm or greater increases in cortical thickness. The researchers found no significant associations between age or type of COVID-19 booster vaccine in patients with > 0.2 cm increases in cortical thickness.

Twenty-three of the 24 patients with cortical thickening > 0.2 cm had follow-up imaging. According to the researchers, there was no detection of ipsilateral breast cancer or axillary malignancy as of December 31, 2022.

“Given the high frequency of lymphadenopathy following COVID-19 vaccination, further evaluation or follow-up may not be necessary in patients without a suspicious finding within the breast,” wrote study co-author Joao Vicente Horvat, M.D., an instructor of radiology at Memorial Sloan Kettering Cancer Center in New York, N.Y., and colleagues. “ … A similar strategy should be considered for patients following the COVID-19 booster vaccination, as the frequency of lymphadenopathy can be considered high, especially during the first 3 weeks after the booster.”

(Editor’s note: For related content, see “Post-Vaccine Axillary Lymphadenopathy: What a New Chest MRI Study Reveals” and “New Study Points to Longer Duration of Axillary Lymphadenopathy After COVID-19 Vaccine.”)

Emphasizing the challenge of diagnosing lymphadenopathy, the researchers noted that breast MRI features associated with lymphadenopathy range from lack of a fatty hilum and irregular contours to a decreased long/short axis ratio. While cortical thickness is the most common morphological feature utilized to diagnose malignant lymphadenopathy, Horvat and colleagues maintained that identifying abnormal lymph nodes is subjective and there is no specific cutoff standard for cortical thickness increase that would be indicative of lymphadenopathy.

For persistent lymphadenopathy after COVID-19 vaccination, the study authors suggest follow-up fine needle aspiration or core needle biopsy. As vaccine-related lymphadenopathy and malignant lymphadenopathy may have some overlapping imaging features, the researchers advocate a higher index of suspicion in patients with elevated risk of malignancy.

“In patients with abnormal lymph nodes and known ipsilateral breast malignancy, lymphadenopathy should not be assumed to represent vaccine-related changes,” emphasized Horvat and colleagues.

In addition to the retrospective nature of the work, the authors said another limitation of the study included variation with the timing of breast MRI after COVID-19 booster vaccination. The researchers also acknowledged a lack of consistent follow-up and noted that some patients did not have follow-up MRI exams. Horvat and colleagues also pointed out that one radiologist made all of the MRI measurements in the study.