How can doctors tell mesothelioma and lung cancer apart?When a person is diagnosed with malignant pleural mesothelioma (MPM), the disease is often very advanced. The same is true of some metastatic lung cancers. Mesothelioma starts in the respiratory system before spreading throughout the chest and, sometimes, the rest of the body. So do some advanced lung carcinomas. Both diseases even cause pleural effusion, or a buildup of fluid in the sac surrounding the lungs.
So how can doctors tell the two apart?
This question was the subject of a study lately published in the journal Thorax. Dr R. Bhardwaj, a researcher at the UK's St. James University Hospital, tackled it by examining the medical records of 101 different patients with respiratory illnesses.
He found that molecular biomarkers often clue in the experts to the source of a pleural disease.
Putting pleural samples under the microscope
Bhardwaj acknowledged that it's not always easy to differentiate MPM from metastatic lung cancer, especially at first blush, before doctors have had a chance to take X-rays and perform MRIs or CT scans.
To determine the best way to categorize pleural diseases, he reviewed the records of 65 people diagnosed with MPM, 25 with metastatic lung cancer and 15 with benign pleural effusions.
After comparing the records, Bhardwaj found that molecular tests of pleural fluid are a good way to tell the conditions apart.
In particular, he pointed to three pleural proteins - CCL2, COL3A1 and galectin-3 - as the biomarkers that best help physicians differentiate between MPM and lung cancer.
Proteins tell all
Bhardwaj explained that, in most cases, high levels of CCL2 and COL3A1 (two proteins associated with inflammation) can help doctors positively diagnose mesothelioma, since patients with metastatic lung cancer had much lower levels than those with MPM.
Likewise, galectin-3, a protein linked to cell growth, was negatively associated with mesothelioma - that is, high levels of galectin-3 tend to indicate that a pleural disease is not MPM, but instead that it is more likely an advanced lung carcinoma.
Of course, a complete diagnosis of mesothelioma usually rests on the results of a number of tests. To start, doctors usually X-ray patients to determine the cause of cough or shortness of breath.
After that, MRIs and CT scans can provide a clearer picture of tumors or pleural effusions. According to the American Cancer Society, physicians then have a number of diagnostic tools that they can use to confirm the presence of MPM. These include pleural fluid analysis, blood tests, needle biopsies and open surgical biopsies.
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