COVID-19 Vaccine-Associated Subclinical Axillary Lymphadenopathy on Screening Mammogram

Acad Radiol. 2022 Apr;29(4):501-507. doi: 10.1016/j.acra.2021.11.010. Epub 2021 Nov 17.


Background: Women who received a COVID-19 vaccination may display subclinical unilateral axillary lymphadenopathy on screening mammography, which can appear suspicious for malignancy, leading to additional diagnostic evaluation.

Purpose: To evaluate the prevalence of subclinical unilateral axillary lymphadenopathy (sLAD) on screening mammogram in women who received either the first or second dose of the Pfizer-BioNTech (Pfizer) or Moderna COVID-19 vaccines compared to women who have not.

Materials and methods: In this IRB-approved, HIPAA complaint study from 12/14/2020 to 4/14/2021, 1027 patients presented for screening mammography and met study inclusion criteria. Patients with history of baseline lymphadenopathy or prior cancer diagnosis were excluded.

Results: Of the 1027 women, 43 were recalled for unilateral sLAD. 34 women received a COVID-19 vaccination ipsilateral to the sLAD (Pfizer n=19, 44.2%; Moderna n=15, 34.9%), 9 did not (20.9%). Incidence of unilateral axillary sLAD was significantly higher (p-value<0.01) in those who received a COVID-19 vaccination within approximately 7 weeks preceding screening mammogram. 13.2% of patients who received the Pfizer vaccine and 9.5% of patients who received the Moderna vaccine developed sLAD. Moderna's vaccine elicited a more robust reaction in the elderly (Moderna 63.7 years vs. Pfizer 59.7 years). For both vaccines, sLAD resolved on average 46.5 days after the last COVID-19 vaccine (p=0.44).

Conclusion: Women who have received either mRNA COVID-19 vaccines may benefit from scheduling their screening mammogram before vaccination or consider delaying screening mammography 8 weeks. While Pfizer may have an overall more robust immune response, Moderna may elicit a stronger immune response in elderly women.

Summary: Women who received a COVID-19 vaccination before screening mammography were significantly more likely to present with subclinical axillary lymphadenopathy than women who did not receive the vaccine.

Key results: 13.2% of women who received a Pfizer-BioNTech vaccine exhibited subclinical axillary lymphadenopathy compared to 9.5% of those who received the Moderna vaccine. Only 1.2 % of those who did not receive a vaccine presented with subclinical unilateral axillary lymphadenopathy. The average time of resolution of the lymphadenopathy on diagnostic mammogram was 46.5 days overall, with Pfizer-BioNTech taking 50.7 days and Moderna 41.5 days.

MeSH terms

  • Aged
  • Breast Neoplasms* / diagnostic imaging
  • Breast Neoplasms* / epidemiology
  • COVID-19 Vaccines / adverse effects
  • COVID-19* / epidemiology
  • COVID-19* / prevention & control
  • Early Detection of Cancer
  • Female
  • Humans
  • Lymphadenopathy* / chemically induced
  • Lymphadenopathy* / diagnostic imaging
  • Lymphadenopathy* / epidemiology
  • Mammography
  • SARS-CoV-2


  • COVID-19 Vaccines