Brief Report Axillary lymphadenopathy after COVID-19 vaccinations in patients with thoracic malignancy: Incidence, predisposing factors, and imaging characteristics

Nishino, Mizuki; Hatabu, Hiroto; Ricciuti, Biagio; Vaz, Victor; Michael, Kesi; Awad, Mark M.

Objective Axillary lymphadenopathy from COVID-19 vaccine is an emerging phenomenon during unprecedented mass vaccinations, which can be incidentally found on CT scans. The present study investigated the incidence, predisposing factors, and imaging characteristics of vaccine-related axillary lymphadenopathy in patients with thoracic malignancy who underwent CT scans before and after COVID-19 vaccinations. Methods The study included patients with thoracic malignancies who received two doses of mRNA-based COVID-19 vaccinations and had pre-vaccine and post-vaccine chest CT scans. Post-vaccine chest CT scans were reviewed for increase in size of axillary/subpectoral lymph nodes, comparing to the pre-vaccine scans. The cases with axillary/subpectoral lymphadenopathy were further reviewed independently by two radiologists referring to clinical information, to determine if lymphadenopathy was attributed to vaccinations. Results Vaccine-related axillary/subpectoral lymphadenopathy was noted in 21 of 232 patients (9.0%). The median short axis diameter of the largest node was 7 mm (range: 5-14 mm). The median number of increased nodes was 4 (range: 1-10). The median time to the post-vaccine scan demonstrating lymphadenopathy was 1.7 weeks (range: -2.9 – 6.6) from the 2nd dose. Vaccine-related lymphadenopathy was noted more commonly in woman than in men (18/144, 12.5% vs. 3/88, 3.4%, respectively; p=0.019), and with mRNA-1273 vaccines than BNT162b2 vaccines (6/28, 21% vs. 15/204, 7.4%, respectively; p=0.026). Conclusions The incidence of lymphadenopathy was 9%, with a median onset time of 1.7 weeks after the 2nd vaccine dose. Female sex and vaccine type (mRNA-1273 vaccine) were associated with higher frequency of lymphadenopathy, providing initial observations to inform further investigations in larger cohorts.