Among patients with thoracic malignancies, lymphadenopathy after COVID-19 vaccination is more common with the Moderna vaccine, according to a study published in the Journal of Thoracic Oncology.

The study included 232 patients with thoracic malignancies who received 2 doses of either the Pfizer-BioNTech vaccine or the Moderna vaccine between December 2020 and April 2021.

Patients had pre-vaccine and post-vaccine chest CT scans. Post-vaccine scans were evaluated for enlargement of lymph nodes in the axilla and subpectoral areas and compared with the pre-vaccine scans.

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Lymphadenopathy cases were reviewed independently by 2 radiologists to confirm that lymphadenopathy was attributable to vaccination.


Vaccine-related axillary lymphadenopathy was observed in 9% of patients (21/232). The median time to onset was 1.7 weeks (range, 2.9-6.6 weeks) after the second vaccination.

The median number of enlarged nodes was 4 (range, 1-10), and the median short-axis diameter of the largest node was 7 mm (range, 5-14 mm). Enlargement of more than 1 node was observed in 17 patients (81%), and enlargement of 5 or more nodes was noted in 6 patients (28%).

Both axilla and subpectoral nodes were enlarged in 11 patients, and 10 patients had enlargement of axillary nodes only.

The incidence of vaccine-related lymphadenopathy was significantly higher among patients who received the Moderna vaccine than among those who received the Pfizer-BioNTech vaccine — 21% and 7.4%, respectively (P =.026).

Vaccine-related lymphadenopathy was also significantly more common in women than in men — 12.5% and 3.4%, respectively (P =.019).

There were no significant differences by age, race, smoking status, tumor type, disease stage, scan timing, or scan type. Furthermore, undergoing a PET/CT scan after vaccination had no significant impact on the incidence of lymphadenopathy (P =.43).

“Considering the needs of frequent serial scanning in patients with cancer, especially for those on active treatment, it is likely more realistic to precisely define the imaging characteristics of vaccine-related lymphadenopathy and establish criteria for accurate diagnosis of the phenomenon, rather than delaying imaging studies that are necessary for treatment decisions,” the researchers wrote.

They are planning to conduct a follow-up study when more patients with longer post-vaccine follow-up are available.

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Nishino M, Hatabu H, Ricciuti B, et al. Axillary lymphadenopathy after coronavirus disease 2019 vaccinations in patients with thoracic malignancy: Incidence, predisposing factors, and imaging characteristics. J Thorac Oncol. 2021;S1556-0864(21)03184-1. doi:10.1016/j.jtho.2021.08.761