Three Ways that Doctors Can Diagnose Mesothelioma

Doctors can’t rely on symptoms alone to tell them whether a patient has mesothelioma. Symptoms can create a suspicion of mesothelioma, but for confirmation they must conduct special tests.

Mesothelioma tests are sophisticated and come in three types. The first type involves the use of imaging technology. The second type entails sampling and analyzing the patient’s blood. The third type of test is one in which suspicious-looking tissues or lumps are surgically removed from the patient’s body and then studied in a laboratory.

Each type of mesothelioma test has advantages and disadvantages. For example, it takes a month or more to obtain a diagnosis from surgical removal of suspect tissues, but only about a week to get back results from a blood draw—and just a couple of days for an imaging test.

But on the flip side, the mesothelioma test type that yields a diagnosis the fastest is not the most completely reliable—the one that’s truly conclusive is the one that takes the longest for results to come back, the surgical removal of tissues.

Imaging studies

The most widely used imaging technology for diagnosing mesothelioma is positron emission tomography (PET).

PET studies can reveal the presence of mesothelioma on the pleura, the pericardium, or the peritoneum.

It works like this. First, the patient is injected with a solution that contains a radionuclide. This is solution containing mildly radioactive particles that the blood stream carries throughout the body.

It takes about 45 minutes to an hour for the radionuclide particles to fully travel the body. During this journey, the particles encounter countless cells. Healthy cells show no interest in the radionuclide, but mesothelioma cells gobble it up.

After the particles have completed their trek, the patient’s body is imaged by the PET machine. This is a scanner that operates on a principle similar to that of an x-ray machine—it sends
photon energy through the body and “sees” anatomic structures and activities by measuring the resistance the photons encounter as they pass through.

The PET scanner easily detects the radionuclide particles (they’re referred to as tracers). Since only mesothelioma cells are interested in consuming these tracers, it’s likely that mesothelioma is present if the scanner picks up large accumulations of the radionuclide particles in places where mesothelioma would be expected—on the pleura, the pericardium, or the peritoneum.

Computed tomography (CT) is another imaging technology that is used, typically to conduct a quick preliminary test. Here, the patient’s body is x-rayed with the resulting imaging data processed through a computer. This permits the showing of far more detail than would be otherwise possible with x-rays alone. CT images also can be generated in three dimensions, which helps doctors better characterize the size and shape of any detected suspicious masses.

Because CT scans show some things a PET scan can’t (and vice versa), imaging doctors routinely request the two types of tests be conducted together. This is feasible because makers of imaging technology have produced hybrid scanners that combine CT and PET in one system. When it comes to diagnosing mesothelioma by imaging, a PET-CT combination scan is considered the standard of care.

Blood screenings and assays

The second way mesothelioma is diagnosed is by means of blood screenings and assays. It so happens that mesothelioma cells give off certain molecules that are picked up by the blood stream. These molecules can be detected in the blood.

To detect these molecules, a sample of the patient’s blood must be collected. This is a simple procedure. The patient sits in a chair equipped with an armrest, then a blood-draw specialist (known as a phlebotomist) inserts an ultra-fine needle in a vein on the patient’s arm to remove a small quantity of blood for testing.

The collected blood is stored in sealed vials and transported to a lab for screening and assaying by technicians skilled in identifying the molecules of mesothelioma. As an aside, the molecules have a technical name: biomarkers.

The results of blood screenings and assays are useful, but not at this time considered reliable enough to yield a definitive mesothelioma diagnosis. Doctors mainly look to mesothelioma blood tests for confirmation that they are on the right track in suspecting mesothelioma.


A biopsy is the best and surest way to tell if a patient has mesothelioma. To perform a biopsy, the doctor must use instruments to probe inside the chest or abdomen and remove a piece of the suspicious growth found there. The removed specimen is then examined under a microscope and cultivated in a lab dish for further observation and testing.

One method of collecting this sample is called an excisional biopsy. Using a surgical knife, a small opening is made to the chest or abdomen and then a special tool is inserted to slice off and extract a small piece of the growth. The doctor makes this opening in a place where access to the suspicious growth will be easiest (the precise location is determined by an imaging test performed beforehand).

Another sample-collection method is fine-needle aspiration. Here, the doctor uses a CT or an ultrasound imaging system to guide the insertion of a thin, syringe-mounted needle into the chest or abdomen. When the needle reaches the suspicious growth, the doctor pulls back on the syringe’s plunger to suction up little bits of tissue.

Doctors also have the option of merely observing the suspect mass rather than removing samples of it. The procedure for this called a thoracoscopy. It entails the surgical insertion of an endoscope, which is a thin, flexible tube with a tiny video camera mounted at the tip. The camera streams live pictures of the interior of the chest cavity or abdominal cavity, giving a real-time look at the mass.

Another biopsy option available to doctors is thoracentesis. This is a procedure for syphoning pleural fluid from the chest cavity. When pleural mesothelioma onsets, it causes the lining around the lungs to overproduce fluid. Some of the cancer’s cells end up in this fluid and can be detected when a specimen of the fluid is examined under a microscope.

Thoracentesis is performed by inserting an imaging-guided needle through the patient’s back; when the needle is properly positioned, a tube is attached to it and the fluid then flows out into a collection vial.

All mesothelioma tests yield crucial information about the cancer. Doctors rely on this information not only to diagnostically confirm mesothelioma but also to help them develop a treatment plan.

Learn more about mesothelioma and how to fight it by downloading this free guide.