Diagnostic pitfalls after COVID-19 vaccination in melanoma and breast cancer patients: A case series

INTRODUCTION: During the current Coronavirus Disease 2019 (COVID-19) pandemic, significant COVID-19 disease-reducing developments have been made, culminating in the COVID-19 vaccines. However, COVID-19 vaccines may complicate oncological staging and follow-up oncological disease course since they may induce the enlargement of lymph nodes. Consequently, this uncertainty may lead to increased distress. PRESENTATION OF CASES: This case series describes seven patients diagnosed with melanoma or breast cancer in whom lymphadenopathy was observed on oncology imaging after COVID-19 vaccination. Four of these patients underwent additional diagnostic testing, all without malignant cells on pathological examination or suspected metastasis on imaging. The remaining patients were re-evaluated, and the lymphadenopathy was interpreted as an adverse outcome of the recent COVID-19 vaccination. In addition, four out of seven patients were vaccinated in the ipsilateral arm relative to the tumor. Abnormal lymph nodes could be observed up to sixty-nine days after COVID-19 vaccination. DISCUSSION AND CONCLUSION: These findings indicate that a COVID-19 vaccination may result in possible false-positive oncological imaging findings in melanoma and breast cancer patients. Moreover, it is advised to administer the vaccine in the contralateral arm of the primary tumor, suspected breast abnormalities, or after the oncologic imaging in melanoma and breast cancer patients.