Mesothelioma Diagnosis
Diagnosing mesothelioma in a patient who is showing symptoms is a multi-step process. It involves discussing the patient’s medical history and past asbestos exposure, along with testing via chest X-rays, CT scans, and biopsies. Since mesothelioma is rare, it is often recommended to obtain a second opinion to ensure a correct diagnosis.
Due to the complexity of the disease, the process of diagnosing mesothelioma often involves a variety of imaging tests, a biopsy—which may be obtained surgically—and sometimes blood tests. Getting a second opinion is often beneficial, as this is a relatively rare cancer.
Challenges in Mesothelioma Diagnosis
The diagnosis of mesothelioma is fairly challenging. This is related to a few different features of this particular cancer.
- The symptoms are nonspecific. “Nonspecific” is a term used in medicine to denote symptoms that can be caused by a wide variety of diseases. The symptoms caused by mesothelioma are nearly identical to those of many other respiratory conditions. Because many of the conditions are far more common than mesothelioma, it may take a while to rule out the more prevalent causes and arrive at the correct diagnosis.
- The latency period is long. The term “latency period” refers to the time period between being exposed to a carcinogen—in this case, asbestos—and developing cancer. For mesothelioma, the latency period is quite long. It can be 20 to 40 years or even longer. By the time they develop mesothelioma, many people have forgotten about their exposure, and may not think to mention it to their doctors.
- The disease is relatively rare. Mesothelioma makes up 0.17% of all cancer diagnoses in the United States, and there are roughly 3,000 cases diagnosed each year. Doctors learn about mesothelioma in medical school, but they are unlikely to encounter the disease during their careers. Many doctors fail to consider mesothelioma a possible diagnosis, particularly early in the diagnostic process.
These factors can contribute to misdiagnosis of mesothelioma and make early detection of this cancer difficult.
- Medically Reviewed By: Patricia Shelton, M.D.
- Legally Reviewed By: Austin Taylor
- Last Modified March 23, 2023
Symptoms of Mesothelioma
When a patient visits their doctor with symptoms, the doctor will need to consider many possible causes, many of which are far more common than mesothelioma.
Patients with malignant pleural mesothelioma may experience symptoms that may also be caused by pneumonia or other respiratory infections, COPD (emphysema), asthma, and lung cancer, including:
Patients with malignant pleural mesothelioma may experience symptoms that may also be caused by pneumonia or other respiratory infections, COPD (emphysema), asthma, and lung cancer, including:
- Cough
- Shortness of breath
- Chest pain
- Trouble swallowing
- Hoarseness of the voice
Patients with any type of mesothelioma may also experience general symptoms that are associated with many types of cancer, and can also occur with other diseases.
These general symptoms include:
These general symptoms include:
- Unexplained weight loss
- Night sweats
- Fever
Likewise, patients with malignant peritoneal mesothelioma may experience symptoms that can be caused by a variety of digestive problems, such as irritable bowel syndrome, Crohn’s disease, diverticulitis, or colon cancer
These symptoms include:
These symptoms include:
- Abdominal pain
- Constipation
- Swelling of the abdomen
- Diarrhea
- Nausea
- Loss of appetite
Testing for Mesothelioma Diagnosis
When a patient visits their doctor with symptoms, the doctor will generally start with discussing a patient’s medical history. They might ask about risk factors for mesothelioma and other cancers, such as asbestos exposure or smoking. They will also perform a physical exam.
Usually, the next step will be to order an imaging study. The specific type will be different for different types of mesothelioma, but commonly it’s one of the following.
Usually, the next step will be to order an imaging study. The specific type will be different for different types of mesothelioma, but commonly it’s one of the following.
Chest X-Rays
Doctors will order chest X-rays for patients with respiratory symptoms. If the patient has pleural mesothelioma, the X-ray may show areas where the pleura is thickened or areas of calcification of the pleura, which indicate inflammation. These changes may be suggestive of cancer but can’t establish what type of cancer it is.
Computed Tomography Scan (CT scan)
This scan produces detailed 3D images that allow doctors to more precisely visualize a tumor and look for any additional tumors. Contrast dye, which is injected into a vein in order to make certain structures more visible, is sometimes used. A CT scan of the abdomen is a common first step in the diagnosis of peritoneal mesothelioma. For patients with pleural mesothelioma, CT scans of the chest are often used to follow up on a concerning finding on a chest X-ray.
Biopsies
Doctors must have the results of a biopsy to definitively diagnose mesothelioma. A pathologist examines this small sample of the tumor tissue under a microscope and subjects it to a variety of tests to look for specific abnormalities in the cells. This is known as cytology, and it can reveal whether the patient has cancer and, if so, what type.
Many types of biopsies are used for diagnosing mesothelioma.
Many types of biopsies are used for diagnosing mesothelioma.
Core Needle Biopsy
If the tumor is close to the skin, then it may be possible to obtain a core needle biopsy. The biopsy sample is taken using a needle passed through the skin into the tumor. Ultrasound may be used to help guide the precise needle placement.
Fluid Biopsy
Some patients have a buildup of fluid around the lungs or in the abdomen. In some cases, a sample of this fluid is analyzed to check for cancer cells.
Thoracentesis
In a thoracentesis, a doctor uses a needle or a catheter (a thin plastic tube) to drain fluid from a pleural effusion, which is a buildup of fluid around the lungs.
Paracentesis
In a paracentesis, the fluid from ascites, or fluid buildup in the abdomen, is drained using a needle or a catheter.
Endoscopic Biopsy
An endoscopic biopsy is a surgical procedure in which small incisions are made and an instrument called a scope is inserted. Using a camera on the end of the scope, the surgeon can visualize the inside of the body. They can also obtain tissue samples through the scope using specially designed surgical instruments.
Thoracoscopy
For pleural mesothelioma diagnosis, the most common procedure is a thoracoscopy. Through small incisions in the chest wall, the surgeon can visualize the inside of the thoracic cavity to look for tumors, and obtain one or more biopsy samples.
Mediastinoscopy
A mediastinoscopy is used. In this procedure, a scope is inserted into the mediastinum, which is the tissue in the center of the chest.
Laparoscopy
Peritoneal mesothelioma diagnosis may involve a laparoscopy, in which the surgeon uses a laparoscope to look around the abdominal cavity and get biopsy samples.
Open Surgical Biopsy
In some cases, when an endoscopic biopsy isn’t enough, an open surgical biopsy may be needed. This involves making a larger incision to allow the surgeon to see the inside of a body cavity directly rather than through a scope. For pleural mesothelioma patients, the procedure used is called a thoracotomy, while for peritoneal mesothelioma, it’s a laparotomy.
It can be difficult to distinguish different types of cancer from each other. It’s important to be certain of the type in order to treat the patient correctly.
For example, lung cancer is treated differently from mesothelioma. To ensure that the diagnosis is correct, a series of blood tests known as immunochemistry may be used. These tests look for particular proteins in the blood, which are sometimes known as biomarkers.
Different types of cancer are associated with rises in different proteins. For example, patients with mesothelioma often show a rise in the level of soluble mesothelin-related peptides (SMRPs).
Although studies have shown that blood tests are not accurate enough for diagnosing mesothelioma on their own, they can be a useful adjunct to other types of testing in order to be certain of the diagnosis.
Tests for Staging
An important part of the diagnostic process is mesothelioma staging, which is the process of determining how advanced the cancer is. Staging is crucial in creating a treatment plan because cancer treatment options are different in an early stage than in an advanced stage.
Doctors may use additional types of imaging studies for staging mesothelioma.
Doctors may use additional types of imaging studies for staging mesothelioma.
Magnetic Resonance Imaging (MRI)
An MRI may be helpful in localizing tumors and checking for additional tumors around the body. MRI scans sometimes involve the use of contrast dye.
Positron Emission Tomography Scan (PET scan)
PET scans use a tracer to look for malignant cells. This is helpful in determining whether the cancer has spread to lymph nodes or has undergone metastasis, or spread to other parts of the body.