Test Result
What an Abnormal PET Scan Actually Means
You got a PET report with abnormal findings and you're trying to decode it before your appointment.
Educational, not diagnostic. This page won't tell you whether you have cancer. It will help you have a more productive conversation with your physician. For emergencies, call 911.
A PET scan looks for areas in the body using more sugar than they should — a hallmark of many cancers, but also of infection, inflammation, recent surgery, or healing tissue.
Reports describe activity using SUV (Standardized Uptake Value). A higher SUV means more uptake, but the number alone doesn't make a diagnosis. Location, pattern, prior history, and how the area looks on the paired CT all matter.
An abnormal PET is a flag, not a verdict. The next step is almost always correlation — comparing to prior imaging — and often a biopsy of the most accessible lesion.
Common causes — most are not cancer
Active infection
Pneumonia, abscess, tuberculosis, and fungal infections all light up on PET.
Inflammation
Rheumatoid arthritis, sarcoidosis, recent vaccines, and inflammatory bowel disease cause uptake.
Healing tissue
Recent surgery, biopsy sites, or radiation can stay 'hot' for weeks to months.
Benign tumors
Some adenomas, fibroids, and thyroid nodules show uptake despite being non-cancerous.
Brown fat or muscle activity
Cold exposure or tension before the scan causes symmetric, harmless uptake patterns.
Malignancy
New cancer, recurrence, or metastasis — confirmed only by biopsy, not by the PET alone.
- Any abnormal PET should be reviewed with the ordering physician within 1–2 weeks
- A new oncologist consultation is warranted when the report uses terms like 'concerning for malignancy' or 'metabolic activity above background'
- Always bring the PET CD/images, not just the report — radiology centers can release images same-day
- Ask for a second-opinion read if findings change major treatment decisions
What a proper work-up looks like
- 1
Side-by-side comparison
Comparing this PET to any prior imaging is often more informative than the new scan alone.
- 2
Targeted biopsy
Usually the most accessible 'hot' lesion is sampled — interventional radiology, surgery, or endoscopy depending on location.
- 3
Tumor markers
Blood tests like CEA, CA 19-9, PSA, or LDH may help interpret findings in context.
- 4
Multidisciplinary review
Complex cases go to a tumor board — radiologists, oncologists, surgeons, and pathologists review together.
Questions worth bringing to your appointment
- What is the most likely cause of each abnormal area on the scan?
- Which lesion are we biopsying first, and why?
- Could this be infection or inflammation instead of cancer?
- Will I need a second-opinion read of the images?
Frequently asked questions
Does an SUV above 2.5 mean cancer?
Not necessarily. SUV thresholds are guidelines, not diagnoses. Infections and inflammation regularly produce SUVs well above 2.5. The pattern, location, clinical history, and biopsy are what decide.
How long does it take to get biopsy results after a concerning PET?
Typically 3–7 business days for routine pathology, longer if special staining or molecular testing is needed. Ask the team to walk you through their timeline so you're not left guessing.
Should I get a second opinion on the PET read?
If the findings change major decisions — surgery, chemo, or a cancer diagnosis itself — a second-opinion read from a subspecialized radiologist is reasonable and often covered by insurance.
Insurance accepted
Coverage details vary by plan. Our care coordinators help verify your benefits before scheduling.
Want a calm, expert opinion on what's going on?
Request a new patient consultation or independent second opinion with Keck Medicine of USC — Newport Beach. Most major insurance accepted.