Abstract
BACKGROUND/AIM: COVID-19 started to spread as a pandemic in December 2019 and COVID-19 vaccination has been initiated worldwide. The efficacy of vaccination has been scientifically proven, but it might cause axillary lymph node swelling. To diagnose patients with axillary lymph node swelling caused by COVID-19 vaccination, we herein reviewed existing literature on this symptom. CASE REPORT: We report the case of a 70-year-old woman with a breast tumour. She had undergone cecum cancer surgery and regular computed tomography (CT). During breast tumour follow-up, she received scheduled CT that indicated severe axillary lymph node swelling mimicking breast cancer metastasis. We performed aspiration biopsy cytology of that lymph node, and determined this was not cancer metastasis but an effect of the COVID-19 vaccine. We confirmed this diagnosis at one month after computed tomography showed that the lymph node swelling had improved. CONCLUSION: Axillary lymph node swelling can occur after COVID-19 vaccination. Therefore, it is important to consider the effect of the COVID-19 vaccination on axillary lymph node swelling when diagnosing breast tumours.