Ultrasound and shear-wave elastography patterns of COVID-19 mRNA vaccine-related axillary, supra and subclavicular lymphadenopathy.

In this pictorial essay, we illustrate the ultrasound appearance of COVID-19 Pfizer-BioNTech vaccine-related lymph node abnormalities, which can occur at different stations ipsilateral to the site of vaccination, after either first or second vaccine dose and can represent a diagnostic dilemma when encountered in patients with underlying conditions. Typically, they appear as enlarged hypoechoic nodes with loss of fat hilum, increased hilar and cortical vascularization at color-Doppler, but low to intermediate cortical consistence at shear-wave elastography. Asymmetric or diffuse cortical thickening is also frequently encountered. They can be observed in patients without and with clinical symptoms, such as armpit pain, fever and fatigue.