A 29-year-old female subject underwent US examination 3 days after receiving the second dose of Pfizer-BioNTech vaccine, due to the rapid occurrence of a palpable lump at the level of the left axilla (same site of vaccine injection), along with fatigue. Multiple, round, hypoechoic axillary lymph nodes (maximum diameter 11 × 10 mm) with no fatty hilum and mild hilar vascularization. Shear-wave elastography revealed a soft consistence (mean values between 6 and 19 kPa). Follow-up US examination performed 5 weeks after the second dose only showed a reduction in lymph node size (maximum diameter 9 × 6 mm) (Fig. ). No pathological lymph nodes were found in both ipsilateral and contralateral supra/subclavicular and cervical stations as well as in the contralateral axilla.
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.