After your PET scan
If It Might Be Infection, — What Test Comes Next?
When a PET scan flags something that could be infection, TB, or cancer, the scan itself cannot tell you which. The next step is a set of targeted tests that narrow the picture — and in most cases, a tissue sample that confirms it.
Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed September 2026
- The scan cannot decide alone — PET detects metabolic activity, not what is causing it. Infection and cancer can look identical on the image.
- TB is very common here — In Telangana and Andhra Pradesh, tuberculosis is among the most frequent causes of a suspicious PET finding.
- Blood tests come first — They narrow the picture before any procedure is needed, and some results are back within days.
- Tissue usually gives the answer — Only laboratory analysis of a biopsy specimen can confirm what the abnormality actually is.
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When a PET finding could be infection or cancer, more imaging cannot decide between them — the next step is almost always a tissue sample. Blood tests can narrow the picture first, but only the laboratory analysis of a biopsy can confirm what the abnormality actually is.
A whole-body PET-CT at CION costs from Rs 10,499 — among the lowest published prices in Hyderabad. Indicative price, as of September 2026.
What happens after a suspicious PET finding?
Your oncologist reviews the full picture
The scan report is read alongside your clinical history, symptoms, and any previous tests. Context matters: where you have been, what symptoms started first, and whether you have had TB or close contact with someone who has.
Blood and microbiological tests are ordered
These may include a full blood count, inflammatory markers, and TB-specific tests such as an IGRA blood test or a Mantoux skin test. If infection is suspected, sputum samples or other microbiological tests may also be sent at the same time.
Your team decides whether a biopsy is needed
If blood tests and clinical history point clearly toward infection, your team may begin treatment first and re-scan to watch the response. If the diagnosis remains uncertain, a tissue sample is the next step — because treatment for TB and treatment for cancer are completely different.
A tissue sample is taken
How it is done depends on where the abnormality is. A CT-guided needle biopsy is common for lymph nodes or lung lesions. A bronchoscopy may be used for lesions inside the airway. For some locations, a short procedure under anaesthesia is needed. Your team will explain the method before you agree to go ahead.
The sample is tested in the laboratory
The tissue is examined under a microscope by a pathologist and may be sent for GeneXpert or AFB culture if TB is suspected. Histopathology results typically come back within about a week. TB culture takes considerably longer because TB bacteria grow slowly.
Your team explains the result and the plan
Once the result is back, your oncologist will go through what it shows and what comes next. If the biopsy is inconclusive, a different biopsy site or method may be recommended before treatment begins.
Does a suspicious PET finding always need a biopsy?
Not always immediately. In some cases, the combination of blood results, imaging pattern, symptoms, and clinical history is strong enough that your team may start treatment for a suspected infection and check the response with a follow-up scan.
But if any uncertainty remains — particularly when the differential includes cancer — tissue is the only way to be certain. Starting the wrong treatment carries real risk, and your team will not do that when a biopsy can settle the question.
If your oncologist recommends a biopsy, it is because the answer genuinely cannot be determined any other way. That is not alarming; it is the responsible path to a diagnosis you can trust.
PET-CT Partner Centres
PET-CT Scan Centres in Hyderabad
CION offers PET-CT scans through 4 trusted partner PET-CT centres across Hyderabad, so you can choose the one closest to you. Call 18002028726 and we’ll guide you to the earliest available appointment.
PET-CT Centre — Punjagutta
PET-CT Centre — Himayatnagar
PET-CT Centre — Narayanaguda
These are partner diagnostic centres within the CION network. Toll-free booking: 18002028726.
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Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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What do the terms in my report and test results mean?
- FDG-avid
- A finding that takes up the radioactive tracer used in PET imaging. It means the area is metabolically active — which happens in both cancer and active infection. The word alone does not tell you which.
- Differential diagnosis
- A list of conditions that could explain a finding. When your report lists TB, lymphoma, and metastasis in the same paragraph, that is a differential — a set of possibilities that further testing will narrow down.
- IGRA
- Interferon-gamma release assay. A blood test that detects the immune response to TB. It is more specific than the older Mantoux skin test and does not require a return visit to read the result.
- GeneXpert
- A rapid molecular test for TB, usually run on sputum or biopsy tissue. It detects TB DNA and checks for rifampicin resistance — often within hours of the sample arriving. CDSCO and WHO recommend it as a first-line diagnostic in India.
- Histopathology
- Microscopic examination of tissue by a pathologist. It can show whether cells are cancerous, inflammatory, or infected, and is the standard method for confirming a cancer diagnosis.
- AFB culture
- A laboratory test that tries to grow TB bacteria from a sample. It is more sensitive than a rapid test but takes several weeks because TB bacteria grow slowly. A positive result confirms TB; a negative result does not always rule it out entirely.
How long does it take to get a definitive answer?
Blood tests and GeneXpert results are typically available within a few days. Histopathology — the microscope examination of a biopsy — usually comes back within about a week once the sample reaches the laboratory.
AFB culture, which grows TB bacteria from the sample, can take several weeks. If your team needs culture results to confirm or rule out TB, they will explain why the longer wait is necessary and what to watch for in the meantime.
Ask your team for a realistic timeline when the biopsy is planned. Knowing when to expect a result reduces the uncertainty of waiting. It is also reasonable to ask who to call if you have not heard within the expected window.
Book a PET-CT at CION from Rs 10,499 — among the lowest published prices in Hyderabad — with an oncologist-reviewed report and a free Rs 950 consultation, across 4 partner centres. Indicative price, as of September 2026.
Explore 94 more Understanding Your PET-CT Report topics
Infection, TB & Inflammation on PET
- Can Tuberculosis Look Like Cancer on a PET Scan?
- Dental Infection and Jaw Uptake on PET
- Fungal Infection and Abscess on PET-CT
- How Long Should You Wait After an Infection Before a PET Scan?
- If It Might Be Infection, What Test Comes Next?
- Inflammation After Injections, Vaccines and Cannulas
- Old Healed TB and Calcified Nodes on PET-CT
- PET-CT for Fever of Unknown Origin
- PET-CT for Suspected Infection in Implants and Prostheses
- PET-CT for Vasculitis and Inflammatory Conditions
- Pneumonia and Recent Chest Infection on PET
- Sarcoidosis on PET-CT: The Great Mimic
- TB or Cancer? How Doctors Tell Them Apart
- Thyroid Uptake on PET: Diffuse vs Focal
False Positives, False Negatives & Pitfalls
- Bladder, Kidney and Ureter Activity on PET
- Bone Marrow Uptake After Growth Factor Injections
- Bowel Uptake: Normal, Inflammation or Something Else?
- Brown Fat Uptake: A Common Cause of Confusing Findings
- Does a Suspicious PET Finding Always Need a Biopsy?
- Getting a Second Read of Your PET-CT Images
- How Often Is a PET-CT Scan Wrong?
- Muscle Uptake After Exercise or Injections
- Thymic and Rebound Uptake in Younger Patients
- Uptake After Radiotherapy: Inflammation or Disease?
- Uptake at a Biopsy or Surgery Site
- What Causes a False Negative on a PET Scan?
- What Causes a False Positive on a PET Scan?
- What Happens If Two Scans Disagree?
- Which Cancers Do Not Show Well on PET-CT?
- Why the Brain Always Lights Up on PET
Incidental Findings
- A Second Unrelated Cancer Found on PET-CT
- An Incidental Bone Finding on PET-CT
- An Incidental Breast Finding on PET-CT
- An Incidental Kidney or Adrenal Finding
- An Incidental Liver Lesion on PET-CT
- An Incidental Lung Nodule Found on PET-CT
- An Incidental Prostate Finding on PET-CT
- An Incidental Thyroid Nodule on Your PET Scan
- Do All Incidental Findings Need Investigation?
- Focal Bowel Uptake: Could It Be a Polyp?
- Incidental Findings on a PET-CT Scan: What They Are
- Incidental Heart Findings on a Cancer PET Scan
- The Cost of Chasing an Incidental Finding
- What to Ask Your Doctor About an Incidental Finding
Reading Your Report: Core Terms
- 'Cannot Be Excluded' and Other Cautious Phrases
- 'Deauville Score' on a Lymphoma PET Report
- 'FDG Avid': What It Means on Your Report
- 'Hypermetabolic': What the Word Actually Means
- 'Hypometabolic' and 'Photopenic' Findings
- 'Impression' vs 'Findings': Which Section Should You Read?
- 'Interval Change' and 'Stable Since Previous Study'
- 'Krenning Score' on a DOTANOC or DOTATATE Report
- 'Lymphadenopathy' on Your PET Report
- 'Metabolically Active Disease': What It Tells You
- 'Metastasis' and 'Distant Spread' on Your Report
- 'Mildly FDG Avid' vs 'Intensely FDG Avid'
- 'No Abnormal FDG Uptake': Is That a Clear Scan?
- 'Physiological Uptake': Normal Areas That Always Light Up
- 'Residual Disease' vs 'Complete Metabolic Response'
- 'Sub-Centimetre Node' and Why Size Matters on PET
- 'Suspicious for Malignancy': How Certain Is That?
- How Long Does a PET-CT Report Take?
- How to Read Your PET-CT Report: A Section-by-Section Guide
- Should You Read Your Own PET-CT Report Before the Consult?
- TNM Staging on a PET-CT Report
- Why Your Report Mentions the Liver and Blood Pool
Response Assessment Scores & Criteria
- Complete Metabolic Response: What It Means
- Deauville Score 1 to 5: The Lymphoma Scale Explained
- End-of-Treatment PET Scan: What It Decides
- How Doctors Judge Whether Treatment Is Working on PET-CT
- Interim PET Scan During Chemotherapy: Why It Is Done
- Metabolic Response vs Size Response: Why They Differ
- PERCIST Criteria: How Metabolic Response Is Measured
- Partial Metabolic Response: Is That Good Enough?
- Progressive Metabolic Disease: What Happens Next
- RECIST vs PERCIST: Size vs Activity
- Stable Metabolic Disease: Good News or Bad?
- Tumour Flare and Pseudoprogression on PET
- What Is a Deauville 3 and Why Is It Ambiguous?
- Why the Scan Says One Thing and You Feel Another
SUV Values Explained
- Comparing SUV Between Two Scans: Is It Meaningful?
- Does a Higher SUV Mean a More Aggressive Cancer?
- Factors That Change Your SUV Reading
- High SUV but Not Cancer: When the Number Misleads
- Is My SUVmax of 4 High? Reading Your Specific Number
- Low SUV but Still Cancer: The PET-Negative Cancers
- SUV in Non-Cancer Conditions
- SUVmax, SUVmean and SUVpeak: What Is the Difference?
- What Is SUV on a PET Scan?
- What Is a Normal SUV Value?
- What SUV Value Indicates Cancer?
- Why Blood Sugar Changes Your SUV Result
- Why Did My SUV Go Down but Not to Zero?
- Why Did My SUV Go Up After Treatment?
Your next step
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Common questions
Frequently asked questions
Can the radiologist tell from the PET scan whether it is TB or cancer?
No — and this is one of the most important things to understand about PET imaging. The scan measures metabolic activity, which is high in both cancer and active infection. The pattern and location can raise or lower the probability of one diagnosis over another, but a report cannot confirm either. That is why the radiologist lists possibilities rather than a single answer, and why further testing is always needed.
What kind of biopsy is needed, and will it hurt?
The method depends on where the suspicious area is. A CT-guided needle biopsy is the most common approach for lymph nodes or lesions near the surface. A bronchoscope is used for areas inside the airway. Both are done under local anaesthesia or sedation; you should expect some discomfort but not severe pain. Your team will explain the planned method, what preparation is needed, and what to expect during recovery before you agree to go ahead.
Can we start TB treatment first to see if it helps, rather than doing a biopsy?
In some situations, when the clinical picture strongly favours TB, your team may take this approach and monitor the response on a follow-up scan. But this is a clinical judgement your oncologist makes based on your full picture — not a step to take on your own initiative. If there is any meaningful possibility the finding is cancer, starting TB treatment delays the correct diagnosis. Ask your oncologist explicitly whether a treatment trial is appropriate in your case, and why.
If the biopsy shows infection, does that mean there is no cancer?
A biopsy that confirms infection from one site answers the question for that site. It does not automatically rule out cancer elsewhere, or in a different part of the same lesion. Your team will interpret the result in the context of your full clinical picture. If the finding explains all the scan abnormalities and matches your symptoms, that is reassuring. If unexplained findings remain, further investigation may still be recommended. Your oncologist will walk you through what the result means for your specific situation.
My report says 'suspicious' but my doctor has not called yet. Should I be worried?
A report that says 'suspicious' means further investigation is recommended — it does not confirm a diagnosis of cancer or anything else. Radiologists use that word when a finding needs more testing to characterise it. The gap between a report and your doctor's call is usually about scheduling and reviewing all results together, not a sign that the news is bad. If you have not heard within the time you were told to expect, call the clinic and ask when your appointment is.
We are also taking Ayurvedic or herbal medicines. Should we tell the team?
Yes — tell your team everything you are taking, including herbal, Ayurvedic, homeopathic, or traditional remedies. Some preparations can interact with the tests being planned or with treatment that may follow. Your team will not judge you for taking them; they need to know in order to plan your care safely. This is especially important before a biopsy, when some supplements can affect bleeding.