Coincidence of Sarcoidosis and a COVID-19 vaccine-associated hypermetabolic lymphadenopathy in a patient with a history of invasive breast cancer: A case report.

Introduction and importance: Vaccine-associated hypermetabolic lymphadenopathy (VAHL) after a COVID 19 vaccination is a common adverse event and also a diagnostic challenge especially in patients with a history of a malignancy. Case presentations: A 47-year-old woman presented with enlarged lymph nodes in the right hilar, subcarinal, and right supraclavicular regions detected by computed tomography as a postoperative follow-up study of thyroid cancer. Fluorine-18 fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) performed 3 weeks later revealed an FDG uptake in those swollen lymph nodes and in the novel lymphadenopathy in the left axilla and left subclavicular regions. Both biopsy specimens from the right supraclavicular and hilar lymph nodes revealed only multiple small granulomas with multinucleated giant cells without malignancy, consistent with sarcoidosis. The left axilla and subclavicular lymphadenopathy detected by the FDG-PET subsequently spontaneously regressed. Clinical discussion: The coincidental occurrence of VAHL and lymphadenopathy in sarcoidosis patients could cause diagnostic confusion especially in those with breast cancer. Conclusion: Sufficient attention should be paid both to the injection site and the time interval between the vaccination and imaging test in the era of nationwide mass vaccinations against COVID 19.