Researchers in Canada say when it comes to distinguishing between mesothelioma and lung cancer, some proteins are more valuable than others.
The team has identified an especially important protein biomarker for mesothelioma. A biomarker is a compound in body fluid or tissue that can act as a signpost for disease.
Understanding the value of this particular protein as compared to other biomarkers may improve the testing process for mesothelioma.
Pleural mesothelioma and lung cancer share many of the same characteristics. Both affect the lungs and both cause similar symptoms. But they are treated differently.
It is not always easy to tell these two cancers apart, even with high-level diagnostic tools. But the biomarker testing completed in Canada may make it easier.
Similarities Between Mesothelioma and Lung Cancer
Pleural mesothelioma is a cancer that starts on the lining around the lungs. It is usually caused by exposure to asbestos. Over time, asbestos fibers work their way deep into the lung tissue and stay there. Tumors that start on the pleural lining can spread to the lungs and other organs.
Lung cancer is centered in the lungs. It can also be triggered by asbestos, but smoking is the most common cause of lung cancer.
Mesothelioma and lung cancer may both show up first as a cough. Over time, it gets harder to breathe and a person may experience chest pain. Both mesothelioma and lung cancer are serious, but mesothelioma is less responsive to treatment.
Being able to tell the difference between these two cancers is critical to starting the right treatment.
Making an Accurate Diagnosis
It is rarely possible to tell the difference between pleural mesothelioma and lung cancer by the symptoms alone. Patients suspected of having one of these cancers usually have a biopsy.
Pathologists use a staining process on the cells called immunohistochemistry. The stains help them tell the difference between cancer cells under a microscope.
Immunohistochemical stains are based on biomarker proteins. Some cancers produce more of one kind of protein and less of another. Scientists have to understand these protein signatures in order to create accurate tests.
Testing for Mesothelioma and Lung Cancer
The Canadian team tested three broad spectrum cancer markers. Claudin-4, Ber-EP4, and MOC-31 are in both kinds of cancer cells.
The researchers compared levels of the three markers in 68 epithelioid mesothelioma samples, 31 sarcomatoid mesothelioma samples, and 147 non-small cell lung cancer samples.
Claudin-4 staining was present in most of the non-sarcomatoid lung cancers. But claudin-4 did not stain any of the epithelioid mesothelioma samples. That means claudin-4 had a true-positive rate of 100 percent for epithelioid mesothelioma. The other two biomarkers were not quite as useful for distinguishing between mesothelioma and lung cancer.
“We conclude that claudin-4 has considerably greater specificity and comparable sensitivity to MOC-31 and Ber-EP4 for separating NSCLC from epithelioid malignant mesothelioma,” write Julia Naso, MD, and Andrew Chung, MD. Both are pathologists at Vancouver General Hospital.
Sarcomatoid lung cancer and sarcomatoid mesothelioma were harder to tell apart. “The use of all three markers may be necessary for sarcomatoid neoplasms given their limited sensitivity,” concludes the report.
Naso, J, and Chung, A. A[ro; 22. 2020. “Claudin-4 Shows Superior Specificity for Mesothelioma vs Non-Small Cell Lung Carcinoma Compared to MOC-31 and Ber-EP4”, Human Pathology, Epub ahead of print, https://www.sciencedirect.com/science/article/abs/pii/S0046817720300770?via%3Dihub