PET Scan Results: What Do Bright Spots Mean for Your Health?

Q: PET Scan Results: What Do Bright Spots Mean for Your Health?

Thank you for your questions. <br>Here are the explanations：<br>Q1. <br>I would like to ask the doctor if the bright spots in positron emission tomography (PET) indicate the presence of unhealthy cells that absorb the injected substances and appear brighter? <br>A： Positron emis

Positron Emission Tomography (PET) Report Issues

Hello Doctor, I have been experiencing a sensation of a foreign body and sharp pain in my oral and pharyngeal walls, which becomes more pronounced when swallowing saliva.
There is also sharp pain and a foreign body sensation in the mucosa near the left base of my tongue, along with inflammatory symptoms that have been intermittently painful for over six months.
Despite undergoing numerous examinations, no definitive cause has been identified.
It has been suggested that this may be related to the bilateral tonsillectomy I had in April or possibly emotional factors.
Since my symptoms have not improved or resolved, I have undergone various tests: in May, a nasopharyngoscopy showed no abnormalities; in June, a thyroid ultrasound revealed no significant issues; in July, an endoscopy showed no abnormalities in the esophagus; in August, another nasopharyngoscopy showed no significant abnormalities, but there was lymphadenopathy at the right base of the tongue.
In mid-August, I opted for a self-paid contrast-enhanced MRI of the head and neck, which indicated specific lymph nodes on both sides of the neck and lymphadenopathy at the right base of the tongue.
In September, another thyroid ultrasound showed no significant abnormalities, and in October, a PET scan revealed a hypermetabolic area behind the base of the tongue.
Since no cause for my throat foreign body sensation, left base of tongue discomfort, or pharyngeal wall pain has been identified, I decided to undergo a self-paid PET scan.
After the examination, the doctor mentioned a brighter area located at the back of the tongue.
When I inquired if this could indicate something serious, the doctor said we would need to monitor for any changes.
I expressed my symptoms and asked if it was on the left side, to which the doctor replied it was not, but likely at the back of the base of the tongue.
However, the doctor could not confirm whether there were cancer cells present, only stating that the area was brighter and uncertain if it indicated cancer or was benign, suggesting it could be due to inflammation or muscle tension.
When I pressed for clarification on whether this could rule out malignancy, the doctor reiterated that we would need to observe for changes and suggested I consult an ENT specialist for further evaluation of that area.
1.
I would like to ask if the bright spot seen on the PET scan indicates the presence of abnormal cells that have absorbed the injected material, resulting in increased brightness?
2.
Given that other tests have not revealed any issues, does the discovery of an abnormality at the base of the tongue on the PET scan increase the likelihood of a problem?
3.
Considering the lymphadenopathy at the right base of the tongue, could the bright spot on the PET scan be due to the enlarged lymph nodes?
4.
What should my follow-up medical arrangements be, or are there any tests that can more definitively determine whether there are cancer cells in my throat or pharyngeal wall?
5.
I have read online that PET scans can have false positives or negatives; how significant is this likelihood?
I apologize for the numerous questions, but I am genuinely worried about the bright spot found on the PET scan, especially since I have been experiencing persistent sensations of a foreign body and sharp pain in those areas.
I hope you can help me analyze my situation, as I feel very lost and helpless.
Thank you very much.

Miss Lin, 40~49 year old female. Ask Date: 2021/10/05

Dr. Zhuang Zhijian reply Nuclear Medicine

Thank you for your questions.
Here are the explanations:
Q1.
I would like to ask the doctor if the bright spots in positron emission tomography (PET) indicate the presence of unhealthy cells that absorb the injected substances and appear brighter?
A: Positron emission tomography/computed tomography (PET/CT) utilizes radiopharmaceuticals that emit positrons (radioactive isotopes) to detect physiological changes in the body.
There are various PET radiopharmaceuticals used in medicine, with fluorine-18 fluorodeoxyglucose (FDG) being the most commonly used in clinical practice in Taiwan.
It detects the metabolic activity of cells in terms of glucose uptake.
Malignant tumors, due to their rapid growth, require more energy and thus exhibit a higher glucose uptake compared to normal cells.
In addition to malignant tumors, inflamed or infected tissues and benign tumors can also show increased glucose uptake.
Therefore, cells that absorb more fluorine-18 fluorodeoxyglucose indicate a stronger ability to uptake glucose, which will be more prominent on imaging.
Based on differences in intensity, size, shape, and location, various differential diagnoses can be made, including malignant tumors, benign tumors, inflammation, and infection.
Thus, bright spots on PET imaging do not necessarily indicate the presence of unhealthy cells.
Q2.
Since other examinations did not reveal any issues, does the discovery of abnormalities at the base of the tongue in the PET scan indicate a higher likelihood of problems?
A: Fluorine-18 fluorodeoxyglucose has a normal physiological distribution in different tissues of the head and neck, such as the soft palate, tonsils, salivary glands, and floor of the mouth.
Based on the intensity, size, shape, and location of the isotope accumulation, different differential diagnoses can be made.
Therefore, it is not possible to determine the likelihood of a problem based solely on a textual description.
Inflammation or muscle tension can indeed lead to increased accumulation of fluorine-18 fluorodeoxyglucose, which will be visible on imaging.
It is recommended to have an ear, nose, and throat (ENT) specialist examine the area at the back of the tongue or to monitor for any changes.
Q3.
Given that there is lymphadenopathy at the right base of the tongue, could the bright spots in the PET scan be due to the enlarged lymph nodes?
A: It is necessary to assess the location of the bright spots on the PET scan in relation to the lymph nodes, their uptake intensity, and the size of the lymph nodes on imaging to make a judgment.
If the lymph nodes are enlarged and exhibit high glucose metabolism (such as in inflammation, infection, or tumors), the PET scan will show more pronounced uptake.
Q4.
What should my follow-up medical arrangements be, or what tests can confirm whether there are cancer cells in the pharyngeal wall of my throat?
A: It is recommended that you have regular follow-ups with an ENT specialist.
Additionally, if you experience any changes in foreign body sensation or pain, you should seek medical attention.
Q5.
I have seen online that PET scans can have false positives or negatives; how likely is this?
A: The sensitivity and detection rates of PET/CT vary for different malignant tumors.
According to a 2008 study from Italy, the accuracy of PET scans in detecting oral squamous cell carcinoma was 84.2%, with a sensitivity of 84.2%.
Another study from Germany in 2021 showed that the sensitivity and specificity for detecting cervical lymph node metastasis from oral squamous cell carcinoma using PET scans were approximately 83.3% and 84.8%, respectively, with a negative predictive value of about 93.3%.
While false negatives and false positives can occur with PET scans for oral cancers, the likelihood is relatively low.
Another American study indicated that when monitoring post-treatment head and neck cancer patients with PET scans, the negative predictive value was greater than 90%, while the positive predictive value was as low as 50%.
After treatment, head and neck cancer patients may experience inflammation in surrounding tissues or healing granulation tissue, leading to increased accumulation of fluorine-18 fluorodeoxyglucose, which can result in a higher rate of false positives.

Reply Date: 2021/10/05

More Info

Understanding the results of a PET scan, particularly when it shows bright spots, can be a source of anxiety, especially when accompanied by persistent symptoms like the ones you describe. Let's break down your questions and concerns regarding the PET scan findings and their implications for your health.

1. What Do Bright Spots Mean?
In a PET scan, bright spots (or areas of increased uptake) indicate regions where there is a higher metabolic activity. This can occur for various reasons, including inflammation, infection, or the presence of cancerous cells. The radiotracer used in PET scans is often absorbed more by cells that are more metabolically active, which is why these areas appear brighter. However, it is crucial to note that not all bright spots indicate cancer; they can also represent benign conditions or inflammation.

2. Interpreting the Findings
The fact that other examinations (like endoscopies and ultrasounds) did not reveal any abnormalities is a positive sign, but the presence of a bright spot in the PET scan does warrant further investigation. While it does raise the possibility of an underlying issue, it does not definitively indicate cancer. The interpretation of these findings should be done in conjunction with your clinical symptoms and other diagnostic results.

3. Lymph Node Enlargement and Bright Spots
Enlarged lymph nodes can indeed contribute to increased uptake on a PET scan. Lymph nodes often react to infections or inflammation, which can lead to increased metabolic activity in those areas. Therefore, the bright spot you see could potentially be related to the lymph node enlargement rather than a malignancy.

4. Next Steps in Medical Management
Given your ongoing symptoms and the findings from the PET scan, it would be prudent to follow up with an ear, nose, and throat (ENT) specialist. They may recommend further imaging studies, such as a biopsy of the lymph node or the area of concern, to obtain a definitive diagnosis. A biopsy can provide crucial information about whether cancer cells are present. Additionally, they may consider other imaging modalities, such as an MRI or CT scan, to get a more detailed view of the area.

5. False Positives and Negatives in PET Scans
It is true that PET scans can yield false positives and false negatives. False positives can occur due to inflammation or infection, which can mimic the appearance of cancer. Conversely, false negatives can happen if a tumor is small or has low metabolic activity. The rate of false positives can vary depending on the specific context and the patient population, but it is a recognized limitation of the technology.
In summary, while the bright spot on your PET scan is concerning, it does not automatically indicate cancer. The best course of action is to continue working closely with your healthcare providers, particularly an ENT specialist, to explore further diagnostic options. They can help clarify the significance of the bright spot in the context of your symptoms and overall health. Remember, early detection and intervention are key in managing any potential health issues, so staying proactive in your follow-up care is essential.

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