Incidence, Timing, and Long-Term Outcomes of COVID-19 Vaccine-Related Lymphadenopathy on Screening Mammography

Objective To determine the incidence, timing, and long-term outcomes of unilateral axillary lymphadenopathy ipsilateral to vaccine site (UIAL) on screening mammography after COVID-19 vaccination. Methods This retrospective, multisite study included consecutive patients undergoing screening mammography 2/8/2021-1/31/2022 with at least one-year of follow-up. UIAL was typically considered benign (BI-RADS 1/2) in the setting of recent (six weeks post-vaccination. Vaccination status and manufacturer were obtained from regional registries. Lymphadenopathy rates in vaccinated patients with and without UIAL were compared using Pearson’s Chi-squared test. Results 44473 female patients (mean 60.4y +/- 11.4y) underwent screening mammography at five sites. 40029 (90.0%) received at least one vaccine dose. 94 (0.2%) presented with UIAL, 1-191 days post-vaccination (median 91.0 [IQR: 37.0-170.0]). Incidence declined from 2.1% to 0.9% to <0.5% after one, two, and three weeks (P<0.01) and persisted up to 36 weeks (P<0.01%). UIAL did not vary across manufacturer (P=0.15). 77/94 (81.9%) were BI-RADS 1/2 at screening. None were diagnosed with malignancy at one-year follow-up. 17 (18.1%) were BI-RADS 0 at screening. At diagnostic work-up, 13 (76.5%) were BI-RADS 1/2, two (11.8%) were BI-RADS 3, and two (11.8%) were BI-RADS 4. Both BI-RADS 4 cases were malignant and had ipsilateral breast malignancies. Of BI-RADS 3 cases, at follow-up, one was biopsied yielding benign etiology, and one downgraded to BI-RADS 2. Discussion Isolated UIAL on screening mammography performed within six months of COVID-19 vaccination can be safely assessed as benign.