Lymphadenopathy in the era of COVID-19 vaccination - an oncological dilemma in diagnostic imaging.

Initial clinical experience with COVID-19 vaccination suggests that approved COVID-19 mRNA vaccines induce a strong immune response and thus cause a significantly higher incidence of axillary lymphadenopathy compared with other vaccines. It can therefore be expected to complicate the diagnosis of patients with overt or suspected mali-gnancy, in whom it may be indistinguishable from malignant node involvement. There is a need for guidelines on the appropriate management of unilateral axillary lymph node enlargement. This article studies the available reports on vaccine-associated lymphadenopathy. It also presents a basic strategy for the assessment of axillary lymphadenopathy based on preliminary recommendations and an algorithm. According to these recommendations, screening should be scheduled before or at least 4-6 weeks after the last dose of the vaccine. This will allow reactive adenopathy to resolve and avoid unnecessary and costly axillary lymph node biopsy. Clear and effective communication between patients, radiologists, referring physician teams, and the general public is the way forward in the management of adenopathy following COVID-19 vaccination. Herein we present 5 cases of lymph node enlargement after mRNA vaccine administration from different authors. Their initial radiological diagnosis raised concerns that they might be metastases. Therefore, radiologists need to include COVID-19 vaccination in the differential diagnosis of patients with unilateral axillary adenopathy. Short-term follow-up of unilateral axillary adenopathy with recent COVID-19 vaccination is an appropriate recommendation.