Evolution of Lymphadenopathy at PET/MRI after COVID-19 Vaccination.

A 56-year-old female with no history of malignancy underwent research cardiac FDG-PET/MRI the day after injection of the second dose of Pfizer-BioNTech COVID-19 vaccine in her left deltoid muscle. PET/MRI demonstrated unilateral left axillary lymphadenopathy with moderately increased FDG-uptake (Figure). Follow-up PET/MRI was performed five-weeks later according to the research protocol, which demonstrated persistent left axillary lymphadenopathy but no FDG-uptake.

Figure:

A 56-year-old female with no history of malignancy underwent research cardiac FDG-PET/MRI: A, The day after injection of the second dose of Pfizer-BioNTech COVID-19 vaccine in her left deltoid muscle axial fused FDG-PET/MRI images show increased FDG-uptake (maximum standard uptake value 5.6) in three enlarged left axillary lymph nodes (maximum short-axis diameter 1.3 cm), closed arrows. Right axillary lymph nodes were normal, open arrows, B, Repeat FDG-PET/MRI five-weeks after the second dose of her COVID-19 vaccine shows that the left axillary lymph nodes are slightly smaller with no FDG-uptake (closed arrows), but these left axillary lymph nodes remain enlarged compared to the contralateral side (maximum short-axis diameter 1.1 cm).

The first two FDA-approved coronavirus disease (COVID-19) vaccines are highly immunogenic, with reports of ipsilateral axillary lymphadenopathy and FDG-uptake post-vaccination (1,2). These images highlight that FDG-uptake might resolve within a few weeks, while lymph node enlargement could persist beyond five-weeks after injection (3). Lymphadenopathy could be more pronounced and last longer after the second vaccine dose (4).

Further evaluation of the prevalence and duration of vaccine-related lymph node changes on imaging is warranted to inform recommendations on the interpretation of ipsilateral axillary lymphadenopathy and FDG-uptake. Knowledge of each patient’s vaccination schedule may help to guide the optimal timing of imaging for cancer screening.