COVID-19 Vaccine Can Cause False Positive Cancer Diagnosis Radiologists, physicians and patients need to be aware of vaccination-related lymph node swelling, especially on mammograms A 37-year-old woman developed a new, palpable left supraclavicular lymphadenopathy lump five days after her first dose of the Moderna COVID-19 vaccine in the left arm. On the day of vaccination, the patient was asymptomatic. This is an example of how the vaccine can mimic cancer and swollen lymph nodes. Read more about this case study. Image used with permission of RSNA. While the mass COVID-19 vaccination effort over the past four months is bringing closer the light at the end of the pandemic tunnel, as with all things in medicine, it is not without a cost. But the cost here will be in terms of added patient anxiety and financial due to potential of additional, needed tests. There have been several alarms in peer-review literature and radiology societies the past couple months that the COVID-19 vaccines cause temporary inflammation and swelling of lymph nodes in some patients. While the experts say this is normal, it can be a major cause for concern if physicians, radiologists and patients are not aware of this vaccine presentation and assume it is a sign of infection or cancer, leading to additional diagnostic testing or followup exams.