PET scan false positive: what it can mean

PET imaging uses a radiotracer such as FDG to show tissues with increased metabolic activity. Infection, inflammation, healing, some medicines, and normal activity in certain organs can also create increased uptake. The scan is interpreted alongside the CT images, symptoms, examination, and previous imaging. An active spot is a finding to investigate, not a diagnosis by itself.

A radiologist may describe the location, shape, and intensity of an area and recommend comparison with another scan or a different test. In some situations, a biopsy is needed to identify cells directly. Read more about the [FDG Radiotracer](/materials/fdg-radiotracer/) and the [PET-CT Scanner](/technology/pet-ct-scanner/).

Ask the imaging team what the finding was, whether it matches the CT appearance, and what explanation is being considered. Bring earlier scans and a list of symptoms, recent infections, procedures, and medicines. Follow the suggested next step, which may be repeat imaging, another form of imaging, or tissue sampling. Do not stop cancer treatment or assume a diagnosis from the scan wording alone.

Contact your treating team promptly if you develop worsening pain, persistent fever, new shortness of breath, confusion, weakness, or rapidly changing symptoms while the result is being clarified. These symptoms need clinical assessment because urgency depends on the symptom and its severity, not on whether a scan looks active.

Which area was active, and what non-cancer causes fit its location? Do the CT images or older scans change the interpretation? What is the next test, and what would it help distinguish? Would a biopsy be useful, and how will the result affect treatment?