After a few months of introducing C-19 vaccines, many cases of false-positive lymph nodes were reported on nuclear PET scans, some of which led to unnecessary biopsies and unnecessary worry for the patients concerned.

According to Mayo Clinic, the positive nodes were on the same side as the vaccine shot in the cases where the injection site was known.  Mayo added that some cases had uptake in the deltoid muscle, which is normally where vaccine injections are given, leading to increased suspicion of false positive in cases where uptake was in both deltoid muscle and axillary lymph nodes (armpit).  At least one case was found in the supraclavicular nodes (clavicle area), but it was noted that might have been a stronger immune reaction due to the patient undergoing immunotherapy.

This issue had come up several times in my large online Facebook group, but the number of threads is dwindling, so perhaps the word is getting around.  I myself encountered this on my own PET scan (Ga68) when a reactive axillary node was found after my Ga68 PET in July 2021. The report noted it as probably related to my recent C-19 vaccine (clear on previous nuclear scans). Further indication that radiologists are on the lookout for such cases.

Further reading:

PET findings after COVID-19 vaccination: “Keep Calm and Carry On” – PMC (nih.gov)

False-Positive Lymph Nodes on PET Scans After COVID Vaccination (medscape.com)