What can a PET scan show about a tumour?

PET adds information about tissue behaviour to the structural detail from CT. A more active area may help show the extent of a known tumour, involved lymph nodes or possible sites elsewhere. It does not directly prove that a spot is malignant, and some tumours show little tracer uptake. Treatment, infection, inflammation and normal organ activity can change the appearance. The radiologist and treating team interpret the pattern, size, location and clinical context together.

Bring the referral details and tell the imaging team about recent biopsy, surgery, radiotherapy, infection or medicines. Follow the preparation instructions and remain still during imaging. Ask whether the result is being used for diagnosis, staging, treatment planning or follow-up. The [PET-CT Scan](/treatments/diagnostics-and-staging/pet-ct-scan/) combines the two image types, and [Lymphoma](/conditions/lymphoma/) is one condition for which PET-CT may be used in care planning.

Call the clinical team if you have a new or rapidly worsening symptom while waiting for the report, rather than relying on the scheduled scan discussion. Seek urgent help for severe breathlessness, collapse, confusion, or sudden severe pain. After the appointment, report concerning symptoms that began with the injection or scan.

Ask whether the scan shows a definite finding or an area needing clarification, whether a biopsy is required, and how recent treatment might affect the image. Ask what result would change your care plan and when you will review it.