There is almost nothing more unfortunate than a mesothelioma diagnosis. When it happens, you may feel as if you’ve been punched in the gut. Many people, however, do not fully understand how mesothelioma is diagnosed. Because of the disease’s relative rarity, a lot of other more common diseases must be ruled out first.
Additionally, mesothelioma is known to have quite a long latency period. This is a term that refers to the length of time from a patient’s first exposure to a disease-causing agent to the moment symptoms start to appear.
We know that long-term exposure to asbestos is the primary cause of mesothelioma, but the latency period between first exposure and the appearance of symptoms can be as long as 30 to 40 years.
So, how do doctors go about diagnosing a disease that effectively hides in the body for decades?
To get an accurate diagnosis, doctors typically run three different types of tests:
- Imaging scans
- Blood tests
Typically, the first course of action is to take a look at the interior of the body using mesothelioma imaging scans. Any patient who complains of symptoms in the chest or abdominal area consistent with mesothelioma will likely get an imaging scan.
Most of these imaging techniques provide a better (although not definitive) look at the affected area. Imaging scans are never enough to make a complete diagnosis, but they can help doctors understand more about what’s going on in your body.
Common imaging techniques include:
- PET scan
Most doctors will start out with an X-ray of the affected area—usually the chest or abdomen. A chest X-ray can identify the presence of a tumor or fluid buildup in and around the lungs in cases of pleural mesothelioma. For peritoneal mesothelioma, doctors will use an X-ray of the abdomen to identify any possible bowel obstructions that could turn out to be tumors.
A computed tomography scan (CT-Scan) uses a collection of X-ray images to produce a 3-dimensional model of a scanned area. The images are taken from numerous angles so that doctors have a full view of the affected area. Because the images have such high contrast, doctors can distinguish between healthy cells and possible mesothelioma or otherwise diseased cells.
An MRI (or magnetic resonance imaging) also creates a 3D model of the scanned area, but it uses radio waves, a powerful magnet, and computer imaging software to create the model.
Patients will be asked to lie down in a cylindrical tube that will create an image of the affected area. MRIs are very helpful both as a diagnostic tool and as a tool to determine how far the disease has spread (or metastasized). MRIs are usually a bit clearer than CT-Scans, as well.
The fourth imaging scan option is the positron emission tomography (PET) scan. These scans are a bit different than the previous three. They work by intravenously injecting a radioactive isotope into the patient’s body. At the time of the injection, the isotope is located within a sugar or glucose molecule.
Because mesothelioma cells require more energy than healthy cells, they will consume radioactive sugar molecule at a faster rate. The PET scanner will then detect and make an image of the area, and specialists can identify whether the extent of tumor growth and whether the disease has spread. PET scans are usually less clear than MRIs but can be valuable in the diagnostic process.
All of these scans (particularly PET, CT, and MRI) are also routinely used throughout the duration of the treatment process. They can essentially provide progress reports for how the disease is reacting to treatments and if those treatments are effective without having to perform major surgery to get a closer look.
Blood Tests and Biomarkers
Like imaging scans, blood tests alone cannot provide a concrete mesothelioma diagnosis. Even so, they can offer an even clearer picture for your doctor to work with.
Biomarkers in the bloodstream play a large role in the efficacy of blood tests. A biomarker is basically a substance in the blood that may indicate the incidence of mesothelioma. Most biomarkers appear naturally in the bloodstream, but, if they are seen at higher levels, then they could indicate mesothelioma.
Some common mesothelioma biomarkers include:
- Soluble mesothelin-related peptides (SMRPs)
- High Mobility Group Box Protein 1 (HMGB1)
Soluble mesothelin-related peptides (SMRPs) are often looked for with a biomarker test (or assay) called MesoMark. Mesothelin itself is a glycoprotein that healthy mesothelial cells produce. It can be found in the blood in small amounts in basically everyone.
For those with mesothelioma (particularly pleural mesothelioma), levels of mesothelin and its variants like SMRPs are usually found at much higher levels in the blood.
Unfortunately, MesoMark is really only effective at identifying the possibility of stage 3 or stage 4 mesothelioma. It has a sensitivity (or probability of positive detection) ranging from 19 to 68%.
N-ERC/Mesothelin (another mesothelin variant) has a much higher sensitivity during blood serum tests at 95%. Combining MesoMark and N-ERC/Mesothlin can produce more accurate results, although neither test is considered good enough for an outright diagnosis.
Osteopontin is another glycoprotein that appears in the bloodstream at high levels for cancer patients. The problem with osteopontin is that it’s non-specific, meaning that patients with a variety of diseases show increased levels of the substance.
The HMGB1 protein is a new biomarker option for mesothelioma patients. Unlike other biomarker assays, HMGB1 can actually identify whether or not an individual has been exposed to asbestos even before they have been diagnosed with mesothelioma. Although clinical trials are still ongoing, the HMGB1 protein may prove to be invaluable for early detection of mesothelioma.
At one point, Fibulin-3 demonstrated a 97% rate of sensitivity for detecting mesothelioma. Subsequent studies, however, have never been able to duplicate that number. Still, the glycoprotein is an important biomarker for mesothelioma diagnoses.
All of these biomarkers can also be used to monitor the progress of the disease as it is being treated. For example, an initial diagnostic biomarker assay might indicate high levels of mesothelioma, but the same assay given 6 months later could indicate much lower levels.
While blood tests and imaging scans can move your doctor in the right direction, a mesothelioma biopsy is the only definitive method for producing an accurate diagnosis. A biopsy essentially involves the removal of tissue or fluid from the affected area.
A pathologist then studies that material to determine all of the following:
- Whether the growth is malignant or benign
- If mesothelioma is present
- The cell type
- Stage of the disease
There are several methods for obtaining sample tissue via biopsy. The different varieties often depend on the location of the disease. They also have varying degrees of invasiveness.
The most common methods for a mesothelioma biopsy are:
- Needle aspiration (thoracentesis, paracentesis, pericardiocentesis)
- Camera-assisted surgery (thoracoscopy, laparoscopy, mediastinoscopy)
- Open surgery (laparotomy, thoracotomy)
Needle biopsies are the least invasive option and can even be performed with only local anesthesia or no anesthesia at all. During this procedure, a small needle is inserted to an area with fluid buildup. The fluid is then retrieved through the needle and secured for study. The medical professional doing the procedure will likely use a fluoroscope, X-ray, ultrasound, or CT scanner to help them identify the right area to draw fluid from.
There are three main types of needle biopsies when it comes to mesothelioma: thoracentesis, paracentesis, and pericardiocentesis. Thoracentesis is the procedure used most often because it is a method to help identify the most common type of mesothelioma (pleural). Built-up fluid is retrieved from the area between the lung and the chest wall.
Paracentesis is a needle biopsy procedure for the diagnosis of peritoneal mesothelioma. It uses a large bore-needle in the abdomen to draw out fluid into a syringe. Sometimes, a large amount of fluid is removed and the physician will attach a catheter to the syringe.
For fluid that builds up between the pericardium (lining of the heart) and the heart itself, doctors will use a pericardiocentesis. This procedure is used for pericardial mesothelioma but may also be performed after metastasis for another form of the disease.
The risks for needle biopsies are minimal, and most patients won’t even feel pain during the procedure. Unfortunately, needle biopsies aren’t often definitive when it comes to diagnoses. In some cases, needle biopsies can show no signs of mesothelioma, but that may not be accurate. The ability to identify mesothelioma properly is increased if cancerous cells are removed during the biopsy.
All of these procedures can also be used as palliative treatments. Removing fluid build-up often reduces symptoms like difficulty breathing and abdominal or chest pain.
Camera-assisted surgical biopsies are minimally invasive, usually requiring only a small incision near the tumor site. This procedure is broadly referred to as an endoscopy. A tube that contains a small camera is inserted through the incision allowing the surgeon to look directly at the tumor within the body. A small portion of the affected tissue is also usually retrieved.
During the surgery, patients are usually provided with general anesthesia, meaning that they will be asleep.
The main types of camera-assisted surgery include:
Small incisions are made in the chest near the ribs. The camera looks at the pleural space, looking to identify pleural mesothelioma. This procedure is sometimes referred to as video assisted thoracoscopic surgery, or VATS.
This procedure occurs in the abdomen. Gas is inserted to make organs more easily visible. Peritoneal mesothelioma is usually suspected if this surgery is applied.
An incision is made in the lower neck, and the mediastinoscope is sent down to the space between the sternum and the lungs. This can be used for pericardial mesothelioma or any form of the disease that has spread to the chest area.
There are two main goals for all these methods. The first is to find definitive proof of the existence of a tumor or growth in the affected area. The second is to remove a portion of that tissue to be studied by a pathologist.
Camera-assisted surgical biopsies are becoming more and more common. As a result, doctors are becoming more proficient and risks are greatly reducing. In some cases, these surgeries can be performed on an outpatient basis, and recovery can take place at home. In very rare cases, damage to organs, infections, or internal bleeding can occur.
In general, however, camera-assisted surgeries are the best biopsy options for mesothelioma. They pose little risk to the patient and are usually capable of getting enough tissue to produce accurate diagnoses.
Open surgery biopsies are the most invasive procedures, and are often prescribed only when the other two types of biopsies are not applicable. Sometimes, tumors are located in places that are inaccessible for needle or camera-assisted biopsies. In other cases, the fluid or tissue retrieved from those two biopsies proved to be inconclusive. Major surgical biopsies are more likely to yield accurate diagnostic results, but they also have inherent risks.
The two most common types of open surgery include the thoracotomy and laparotomy. A thoracotomy occurs in the chest while a laparotomy occurs in the abdomen. Both surgeries give doctors a close-up view of any affected internal organs. In fact, these surgeries are sometimes described as “exploratory” because they allow surgeons to see how far the disease has progressed. This is useful in ascribing a stage to the disease.
During a diagnostic thoracotomy or laparotomy, some doctors may opt to perform surgical resections so that the patient doesn’t have to undergo two separate surgeries. In this circumstance, pathological tests are done very quickly to determine if the tissue is malignant.
Because this is a major surgery, the recovery time is usually much longer and often requires a hospital stay. But, this usually ensures that a proper diagnosis can be made.
Pathology is basically the study of the nature of cells, tissues, and fluids. Mesothelioma pathology is unique among all cancers, but it’s also very uncommon. When biopsies are retrieved, the material is sent to a pathologist who looks to make a diagnosis based on them.
Without high-quality pathology, the diagnosis of mesothelioma would all be guesswork.
Pathology can be further broken down into two categories: histology and cytology. Histology describes the study of the anatomy of cells and tissues, including the function and structure of those materials.
The main goal of histology is to discover the cell type of the disease. It is usually used after a tissue biopsy retrieved via some form of surgery.
Mesothelioma has three main cell types, including:
accounts for 50 to 70% of all mesothelioma cell types. Occurs most often in the pleural form of the disease and is considered the least aggressive cell type.
accounts for 10 to 20% of all mesothelioma cell types. Occurs most often in the peritoneal form of the disease and is considered the most aggressive cell type.
accounts for 20 to 40% of all cases. Occurs most often in the peritoneal form of the disease and is a combination of epithelioid and sarcomatoid cells. Aggressiveness depends on the amount of epithelioid cells compared to sarcomatoid cells
Cytology, on the other hand, is more interested in determining how the disease will progress and how it has already progressed. It also looks at how the individual cells are working together, how they’re forming, and how they’re spreading. Cytologists usually look at fluid biopsies to make their determinations.
Pathology as a whole is used to help doctors determine staging (a measure of how far the disease has spread) and prognosis (how they think the disease will progress). With these, they can also determine how best to treat mesothelioma and how long a patient has left to live (life expectancy).
Even with all these diagnostic methods, mesothelioma often goes undiagnosed or gets misdiagnosed. We know that mesothelioma takes a long time to start showing any symptoms which means that it’s often not diagnosed until the later stages. But, even after the whole battery of diagnostic tests are performed, mesothelioma’s rarity leaves it open to misdiagnosis.
Doctors (especially ones who aren’t mesothelioma specialists) are more prone to diagnosing mesothelioma as more prominent but similar cancers like adenocarcinoma or ovarian cancer. Mesothelioma’s symptoms are non-specific, meaning that they could mimic a wide variety of ailments. Physicians who are unfamiliar with mesothelioma may not even consider it as a diagnostic option.
If you suspect that you or a loved one has mesothelioma, it’s important to inform your doctor of any past exposure to asbestos. Remember that mesothelioma’s latency period can be as long as 50 years. So, even exposure to asbestos you experienced as a child will be relevant in the diagnostic process.