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False-positive tumor markers: where is the line between alarm and accuracy?
Tumor markers have become an important tool in modern laboratory diagnostics. Thanks to them, the doctor can obtain preliminary information about the probable presence of a tumor. However, the word “probable” itself plays a key role: the results of these tests do not always indicate oncology. In some cases, the body gives a false signal — the so-called false-positive result. This leads to unnecessary stress, excessive diagnosis, or even unfounded treatment decisions.
What is a false positive result?
A false-positive result is a situation where a tumor marker shows an excess of the norm, but there is actually no tumor. Such an analysis response is often associated not with oncology, but with inflammatory, autoimmune, infectious or even physiological conditions.
Typical examples of false positive markers:
| Tumor marker | Possible non-oncological causes of the increase |
|---|---|
| CA-125 | Endometriosis, menstruation, ovarian cyst, cirrhosis |
| PSA (prostate specific antigen) | Prostatitis, prostatic hyperplasia, catheterization |
| CA 19-9 | Chronic pancreatitis, cholestasis, gallstone disease |
| AFP (alpha-fetoprotein) | Pregnancy, hepatitis, cirrhosis |
| CEA (carcinoembryonic antigen) | Inflammatory bowel disease, smoking, chronic gastritis |
1. Physiological changes
Certain phases of the menstrual cycle, pregnancy, and the patient's age can all affect the level of tumor markers. For example, CA-125 in women increases during ovulation.
2. Comorbidities
Autoimmune disorders, hepatitis, pancreatitis, and cirrhosis can change the concentration of substances in the blood that are considered tumor markers.
3. Technical factors
Errors in blood collection, improper storage of biomaterial, or reagent reactions sometimes cause distortion of the result.
4. Drug treatment
Some drugs, particularly hormonal or immunomodulators, can cause an increase in tumor markers without the presence of a tumor.
Consequences of false results
A false-positive tumor marker can cause anxiety, unnecessary instrumental examinations (CT, MRI, biopsies), waste of time and money, and in some cases even unnecessary surgery. That is why laboratory indicators should always be interpreted only in conjunction with the clinical picture.
How to avoid misinterpretation?
Tumor markers not used for screening healthy people without symptoms.
The analysis should be repeated if there are no other clinical signs.
It is imperative to inform the doctor about concomitant diseases, medications, and previous infections.
To confirm the suspicion, imaging methods are used: ultrasound, CT, MRI, endoscopy, biopsy.
The most accurate approach is monitoring in dynamics: assessment of marker changes over time.
Example from clinical practice
A 42-year-old patient was found to have elevated CA-125. The initial finding was suspected ovarian cancer. However, ultrasound and MRI revealed only endometriosis. After treatment, the tumor marker decreased to normal. This case highlights the importance of avoiding hasty conclusions.
False-positive results are a challenge for both the doctor and the patient. On the one hand, tumor markers are a powerful diagnostic tool, on the other hand, they are a source of potential diagnostic errors. The key principle is not to evaluate the result in isolation. Only a combination of laboratory data, history, clinical examination and imaging provides a reliable diagnosis.
