The only way to confirm a mesothelioma diagnosis is through a biopsy, which can be an invasive and painful procedure. Therefore, doctors use other diagnostic tools, such as imaging scans and blood tests, to assess the likelihood of a mesothelioma diagnosis before performing a biopsy.
Understanding Your Mesothelioma Diagnosis
If you or a loved one has been diagnosed with mesothelioma, you may have many questions running through your head:
- How did I get this terrible disease?
- Should I get a second opinion?
- What does this diagnosis mean for me, my family, and others that I care about?
- Could I have been misdiagnosed?
- How will I be able to pay for treatments?
These and similar questions are perfectly natural. The best way to get information about your specific situation is to connect with a mesothelioma doctor who can answer your questions.
How Mesothelioma Is Diagnosed
The symptoms of mesothelioma can take a long time to develop – often decades. When symptoms do finally appear, they can mimic other illnesses and diseases. For both of these reasons, diagnosing mesothelioma is a difficult process that can take months and many different tests.
In most cases, cancer specialists will approach a mesothelioma diagnosis by first testing to see if another, more common disease is causing the symptoms. As part of this process, the doctor will obtain a full medical history from the patient, which may include asking about any exposure to asbestos.
From there, the doctor will usually perform a series of tests, starting with the least invasive (and, in most cases, least costly), such as imaging scans and blood tests. If these initial tests indicate a potential for mesothelioma, a biopsy will be taken to confirm the diagnosis. Only a histological examination – that is, inspection of biopsied tissue under a microscope – can verify a mesothelioma diagnosis.
The Importance of Early Detection
Mesothelioma has a poor prognosis. However, many studies of the disease have shown that early detection and diagnosis can significantly improve the chances of survival. Catching mesothelioma before it spreads can increase the effectiveness of treatments, as well as open opportunities to try more aggressive treatments that might not otherwise be available.
As a result, much of the research and development around mesothelioma has focused on improving detection and diagnosis of the disease. This includes recent developments of new biomarker blood tests, which can detect the presence of substances that indicate mesothelioma may be present in the body.
Mesothelioma Diagnostic Tests
There are three main types of tests used to diagnose mesothelioma: imaging scans, blood tests, and biopsies. Doctors typically perform the least invasive tests first, followed by more involved tests if they are warranted.
Diagnostic imaging tests, like X-rays, CT scans, and MRIs, help doctors obtain information about the cancer, including how far it has progressed. Each method has its benefits and limitations.
Diagnostic Imaging Tests
X-rays are commonly used to diagnose many conditions, illnesses, and injuries. They can be particularly helpful in finding fluid in the lungs, often an early sign of mesothelioma.
Computer Tomography (CT) scans provide a series of X-ray images to form a 3D image, allowing tumors to be spotted more easily.
Magnetic Resonance Imaging (MRI) scans provide a 3D model with much higher resolution than other imaging methods. This can be helpful in diagnosing metastasis (spreading) of the mesothelioma.
Positron Emission Tomography (PET) scans use a radioactive isotope injection that can be viewed by the scanner. PET scans can help distinguish benign versus malignant tumors.
Blood Tests and Biomarkers
In recent years, a number of blood tests have been developed to identify substances in the blood that can point to the presence of mesothelioma cancer cells. The presence of these substances, known as biomarkers, do not always indicate a mesothelioma diagnosis, but they can provide useful information that can demonstrate a need for a biopsy. Biomarker tests are also known as “assays.”
This assay looks for the presence of mesothelin, a glycoprotein (sugar and protein molecule) that is produced in excessive amounts by mesothelioma cells. Specifically, MESOMARK® tests for soluble mesothelin-related peptides (SMRPs), which are created when mesothelin is dissolved in the bloodstream.
Another byproduct of mesothelin, N-ERC/Mesothelin is a protein fragment that is soluble in the blood stream. Early tests showed a 95% sensitivity for the assay, potentially making it one of the most accurate blood tests for mesothelioma, if the results can be confirmed.
As another glycoprotein, Fibulin-3 is similar to mesothelin as it is produced in higher concentrations by mesothelioma cells. However, existing research has shown irregular results, with some question as to the accuracy of the test. Fibulin-3 assays may nonetheless be useful in distinguishing between malignant and benign lung diseases.
Recent studies have shown that testing for a certain protein – high mobility group box protein 1 (HMGB1) – can not only positively detect individuals with mesothelioma, but also can identify individuals who have been exposed to asbestos but have not yet developed the disease. Additional trials are needed to confirm the results.
Osteopontin, which is a glycoprotein like mesothelin, is also produced in high amounts by mesothelioma. Unfortunately, this particular biomarker is a less accurate diagnostic tool than other assays, as osteopontin is also produced by other types of cancer, as well as kidney stones and ischemic stroke.
A biopsy is an important diagnostic procedure recommended by doctors for patients presenting with signs and symptoms of mesothelioma who have a history of asbestos exposure. Some biopsies can be minimally invasive (e.g., fine-needle aspiration) while others can involve a major surgical procedure (e.g., thoracoscopy).
The general purpose of a biopsy is to obtain a sample of the cancerous tissue. This tissue is then examined under a microscope by a histologist, who can determine whether the tumor is mesothelioma, some other cancer, or another disease altogether.
The least invasive way to obtain a biopsy is through fine-needle aspiration, which draws fluid containing the cancer cells to be studied. In many cases, needle biopsies are insufficient to gather enough tissue for analysis.
Types of needle biopsies:
Through minimally invasive surgery, doctors can use a small tube with a camera in it to view and retrieve sample tissue from the patient.
Types of camera-assisted biopsies:
Mesothelioma is Commonly Misdiagnosed
Mesothelioma is often misdiagnosed, at least initially, partly due to the fact that many mesothelioma symptoms resemble the symptoms of other diseases. Also, because mesothelioma is so rare, doctors may be more inclined to diagnose a more common disease first, thereby delaying treatment. Misdiagnosis can differ depending on the type of mesothelioma a person has. The table below provides common misdiagnoses based on mesothelioma type.
- Bronchial infections
- Chronic Obstructive Pulmonary Disease (COPD)
- Adenocarcinoma and other lung cancers
- Irritable Bowel Syndrome (IBS)
- Crohn’s Disease
- Ovarian cancer
- Other cancers affecting abdominal organs
- Coronary artery disease
- Heart failure
- Tuberculosis pericarditis
- Other heart-related cancers, such as synovial sarcoma
Diagnosing and treating mesothelioma. American Lung Association website. http://www.lung.org/lung-health-and-diseases/lung-disease-lookup/mesothelioma/diagnosing-treating-mesothelioma.html.
Napolitano A, Antoine DJ, Pellegrini L, et al. HMGB1 and its hyperacetylated isoform are sensitive and specific serum biomarkers to detect asbestos exposure and to identify mesothelioma patients. Clinical Cancer Research. 2016;22(12):3087-96. doi: 10.1158/1078-0432.CCR-15-1130.
Malignant Mesothelioma Treatment (PDQ®)–Health Professional Version: Diagnosis and prognostic factors. National Cancer Institute website. http://www.cancer.gov/types/mesothelioma/hp/mesothelioma-treatment-pdq#link/_134_toc. Updated August 7, 2015.
van Zandwijk N, Clarke C, Henderson D, et al. Guidelines for the diagnosis and treatment of malignant pleural mesothelioma. Journal of Thoracic Disease. 2013;5(6):E254-307. doi: 10.3978/j.issn.2072-1439.2013.11.28.