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

Abstract

Background COVID-19 vaccination-related axillary lymphadenopathy has become an important problem in cancer imaging. Data are needed to update or support imaging guidelines for conducting appropriate follow-up. Purpose To investigate the prevalence, predisposing factors, and MRI characteristics of COVID-19 vaccination-related axillary lymphadenopathy. Materials and Methods Prospectively collected prevaccination and postvaccination chest MRI scans were secondarily analyzed. Participants who underwent two doses of either the Pfizer-BioNTech or Moderna COVID-19 vaccine and chest MRI from June to October 2021 were included. Enlarged axillary lymph nodes were identified on postvaccination MRI scans compared with prevaccination scans. The lymph node diameter, signal intensity with T2-weighted imaging, and apparent diffusion coefficient (ADC) of the largest enlarged lymph nodes were measured. These values were compared between prevaccination and postvaccination MRI by using the Wilcoxon signed-rank test. Results Overall, 433 participants (mean age, 65 years ± 11 [SD]; 300 men and 133 women) were included. The prevalence of axillary lymphadenopathy in participants 1-14 days after vaccination was 65% (30 of 46). Participants with lymphadenopathy were younger than those without lymphadenopathy (P < .001). Female sex and the Moderna vaccine were predisposing factors (P = .005 and P = .003, respectively). Five or more enlarged lymph nodes were noted in 2% (eight of 433) of participants. Enlarged lymph nodes greater than or equal to 10 mm in the short axis were noted in 1% (four of 433) of participants. The median signal intensity relative to the muscle on T2-weighted images was 4.0; enlarged lymph nodes demonstrated a higher signal intensity (P = .002). The median ADC of enlarged lymph nodes after vaccination in 90 participants was 1.1 × 10^-3 mm²/sec (range, 0.6-2.0 × 10^-3 mm²/sec), thus ADC values remained normal. Conclusion Axillary lymphadenopathy after the second dose of the Pfizer-BioNTech or Moderna COVID-19 vaccines was frequent within 2 weeks after vaccination, was typically less than 10 mm in size, and had a normal apparent diffusion coefficient. © RSNA, 2022.

Graphical abstract

Figure 1:

Flowchart of participant inclusion and exclusion.

Figure 2:

Bar chart shows the number of participants with and without COVID-19 vaccination-related axillary lymphadenopathy according to the number of days after the second vaccination dose. The prevalence of COVID-19 vaccination-related axillary lymphadenopathy in participants at 1–14, 15–28, 29–42, and 43–56 days after vaccination was 65%, 40%, 29%, and 18%, respectively. The prevalence of lymphadenopathy was less than 10% 57 days or more after vaccination.

Figure 3:

(A) Scatterplot shows the number of enlarged lymph nodes according to the number of days after COVID-19 vaccination. Five or more enlarged lymph nodes were noted in eight of the 433 participants (2%), and those in six of the eight participants were noted 1–14 days after vaccination. (B) Scatterplot shows the short-axis diameter of the largest enlarged lymph node according to the number of days after COVID-19 vaccination. Only four of the 433 participants (1%) had enlarged lymph node greater than or equal to 10 mm in the short axis. (C) Scatterplot shows the long-axis diameter of the largest enlarged lymph nodes according to the number of days after COVID-19 vaccination.

Figure 4:

(A) Scatterplot shows the relative signal intensity on T2-weighted images of the largest enlarged lymph node according to the number of days after COVID-19 vaccination. The relative signal intensity was calculated by dividing the signal intensity of the lymph node by the signal intensity of the pectoralis minor muscle. (B) Scatterplot shows the apparent diffusion coefficient of the largest enlarged lymph node according to the number of days after COVID-19 vaccination (C) Graph shows changes in the relative signal intensity on T2-weighted images of the largest enlarged lymph node between prevaccination and postvaccination MRI in the 11 participants with axillary lymphadenopathy whose corresponding lymph node had a short-axis diameter greater than or equal to 5 mm at prevaccination MRI. The largest enlarged lymph node on T2-weighted images at postvaccination MRI demonstrated a higher relative signal intensity than the corresponding lymph node on T2-weighted images at prevaccination MRI (P = .002). (D) Graph shows changes in apparent diffusion coefficient (ADC) values of the largest enlarged lymph node between prevaccination and postvaccination MRI in the same 11 participants. Changes in the ADC demonstrates the absence of a pattern (P = .17).

Figure 5:

Images in a 50-year-old man 10 days after COVID-19 vaccination. (A, B) Axial T2-weighted image (A) and diffusion-weighted image (B) obtained at postvaccination MRI demonstrate an enlarged lymph node (arrows) in the left axilla ipsilateral to the vaccinated site. (C, D) Axial T2-weighted image (C) and diffusion-weighted image (D) obtained at prevaccination MRI demonstrate the corresponding lymph node (arrowheads). The enlarged lymph node on the postvaccination MRI scans is obviously larger than the corresponding lymph node on the prevaccination scans. The enlarged lymph node on the T2-weighted image at postvaccination MRI demonstrates a higher signal intensity than the corresponding lymph node on the T2-weighted image at prevaccination MRI.

Figure 6:

Images in a 53-year-old man 42 days after COVID-19 vaccination. (A, B) Axial T2-weighted image (A) and diffusion-weighted image (B) obtained at postvaccination MRI demonstrate an enlarged lymph node (arrow) in the left axilla ipsilateral to the vaccinated site. (C, D) Axial T2-weighted image (C) and diffusion-weighted image (D) obtained at prevaccination MRI demonstrate the corresponding lymph node (arrowhead). The enlarged lymph node on the postvaccination MRI scans is larger than the corresponding lymph node on the prevaccination scans. In this participant, the enlarged lymph node on the T2-weighted image at postvaccination MRI demonstrates isointensity relative to the corresponding lymph node on the T2-weighted image at prevaccination MRI.