A 28-year-old female subject underwent US examination 2 days after receiving the second dose of Pfizer-BioNTech vaccine due to palpable left axillary lump and ipsilateral armpit pain (same side of vaccine injection). She also experienced fatigue and headache. US showed the presence of axillary lymph nodes (maximum diameter 14 × 9 mm) with preserved fatty hilum, but diffuse cortical thickening (10 mm) and vivid hilar and cortical vascularization. A soft consistence of the cortex was found at shear-wave elastography (mean values between 3.4 and 8.1 kPa). No pathological lymph nodes were found in ipsilateral supra and subclavicular lymph node stations as well as in lymph nodes contralateral to the site of vaccine injection. Follow-up US examination was performed after 4 weeks and a reduction of lymph node size (7 × 6 mm), cortical thickness (2.9 mm) and vascularization was found (Fig. ).
US examination was performed in a 33-year-old woman with the occurrence of axillary pain and a palpable lump in the supraclavicular region 8 days after the first dose of Pfizer-BioNTech vaccine. The patient had also experienced fever and fatigue right after vaccine injection. Both axillary and supraclavicular lymph nodes were found enlarged (maximum diameter 14 × 6 mm), with no fatty hilum, increased vascularization and soft-intermediate consistence at shear-wave sonoelastography (Fig. ). No pathological lymph nodes were found in the contralateral axilla. US lymph node features were substantially stable at US examinations performed after 3 weeks.