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Mesothelioma and Metastatic Cancer: New Test Can Reliably Tell the Difference

mesothelioma and metastatic cancer

Italian scientists have come up with what they believe is a nearly foolproof way to tell the difference between mesothelioma and metastatic cancer. 

Malignant mesothelioma is a membrane cancer caused by asbestos exposure. Metastatic cancer can start anywhere in the body. It can cause tumors on the pleural membrane that may be mistaken for mesothelioma. 

It is important for doctors to distinguish between these two types of malignancies. Mesothelioma and metastatic cancer are often treated differently. The Italian researchers say two biomarkers may make it easier to know which is which. 

The Difference Between Mesothelioma and Metastatic Cancer

Metastatic cancer or metastatic carcinoma is cancer that has spread to another part of the body from where it started. This usually happens via the lymphatic system. Once cancer cells are in the lymph nodes, they can travel elsewhere in the body and seed new tumors. 

Pleural mesothelioma starts on a membrane called the pleura. Mesothelioma and metastatic cancer on the pleura look very similar. But the drugs doctors use to combat metastatic breast or colon cancer tumors on the pleura are different from the ones used to fight pleural mesothelioma.

Correctly identifying the cancer type and choosing the right drug is especially critical with mesothelioma. It is one of the fastest growing cancers and is almost always fatal. 

Two Key Biomarkers: CRLA-4 and BAP1

All tumors, including mesothelioma and metastatic cancer, contain clues to their origins. These are usually proteins. Scientists call these signposts “biomarkers”. Biomarkers may appear in the blood or other body fluids or in tissue. 

In the new report, Italian researchers focused on a 2-part panel that tests for the proteins Claudin-4 and BAP1. They used samples of lung fluid and tumor tissue from three groups of people: 49 cases of pleural mesothelioma, 49 people with benign growths on the pleura, and 49 people with cancer than had spread to the pleura. 

The differences between mesothelioma and metastatic cancer were clear.

“Claudin-4 strongly stained all metastatic carcinomas and tested completely negative in normal mesothelium, benign reactive mesothelial hyperplasia, and malignant mesothelioma,” reports lead study author Livia Bernardi

All but one of the metastatic cancer samples tested positive for BAP1, too. But BAP1 was low or missing in 88 percent of the mesothelioma cell samples. 

Together, the two-part “Brescia panel” offers a simple but powerful way to distinguish between mesothelioma and metastatic cancer. 

“Double negativity was evident in all malignant mesotheliomas, and double positivity was observed in all metastatic carcinomas,” the researchers write. “This 2-hit panel is probably the best compromise for differentiating malignant mesothelioma and metastatic carcinoma on either cytology [fluid sample] or biopsy specimens.”

A thorough work history is another major part of mesothelioma diagnosis. Almost all mesothelioma patients can trace their disease to asbestos exposure. 


Bernardi, L, et al, “The ‘Brescia panel’ (Claudin-4 and BRCA-associated protein 1) in the differential diagnosis of mesotheliomas with epithelioid features versus metastatic carcinomas”, October 12, 2020, Cancer Cytopathology, Epub ahead of print, https://acsjournals.onlinelibrary.wiley.com/doi/10.1002/cncy.22368

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