Axillary Lymphadenopathy after Pfizer-BioNTech and Moderna COVID-19 Vaccination: MRI Evaluation.

Abstract

BackgroundCOVID-19 vaccination-related axillary lymphadenopathy has become an important problem in cancer imaging. Data is needed to update or support imaging guidelines for conducting appropriate follow-up.PurposeTo investigate the prevalence, predisposing factors, and MRI characteristics of COVID-19 vaccination-related axillary lymphadenopathy.Materials and MethodsProspectively collected pre-vaccination and post-vaccination chest MRI scans were secondarily analyzed. Participants who underwent two doses of Pfizer-BioNtech or Moderna COVID-19 vaccine and chest MRI from June to October 2021 were included. Enlarged axillary lymph nodes were identified on post-vaccination MRI comparing with pre-vaccination MRI. Lymph node diameters, signal intensity on T2-weighted images (T2WIs) and apparent diffusion coefficient (ADC) of the largest enlarged lymph node were measured. These values were compared between pre-vaccination and post-vaccination MRI with the Wilcoxon signed-rank test.ResultsWe evaluated 433 participants (mean age ± standard deviation, 65 years ± 11 years), 300 males and 133 females. The prevalence of axillary lymphadenopathy in participants 1-14 days after vaccination was 65% (30/46). Participants with lymphadenopathy were younger than those without lymphadenopathy (p < 0.001). Female sex and Moderna vaccine were predisposing factors (p = 0.005 and p = 0.003, respectively). Five or more enlarged lymph nodes were noted in 2% (8/433). Enlarged lymph nodes ≥ 10 mm in the short axis were noted in 1% (4/433). The median signal intensity relative to the muscle on T2WI was 4.0. Enlarged lymph nodes demonstrated a higher signal intensity on T2WI (p = 0.002). The median ADC of enlarged lymph nodes post vaccination was 1.1 × 10−3 mm2/sec with the range 0.6 – 2.0 × 10−3 mm2/sec in 90 participants, and thus ADC remained normal.ConclusionAxillary lymphadenopathy after the second dose of Pfizer-BioNtech or Moderna COVID-19 vaccination was frequent within two weeks after vaccination, was typically less than 10mm in size, and had normal ADC. An earlier incorrect version of this article appeared online. This article was corrected on September 14, 2022.