Diagnosis

Doctors use many tests to diagnose cancer and determine if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
  
  
• The type of cancer suspected
  
  
• Severity of symptoms
  
  
• Previous test results

The diagnosis of mesothelioma is challenging. The diagnosis can be difficult to determine, or it can be confused with other diseases, such as lung cancer.

Many people first note symptoms of mesothelioma when they develop fluid in the space around the lungs (called pleural effusion). When this fluid is removed, it can be analyzed to see if there are cancer cells in it. However, testing this fluid is usually not the only test needed to diagnose the disease.

Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. The sample removed from the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). Typically, a biopsy is required to confirm a diagnosis of mesothelioma. In some cases, a needle can be used to get a sample of the lining. More often, though, a surgical procedure (such as a video thoracoscopy) is performed to examine the chest cavity and take tissue samples.

The following procedures may be used to help develop a treatment plan:

Physical examination. A physical examination may include a medical history of the person and his or her family's past illnesses, inventory of their risk factors (including asbestos exposure), and an examination for other signs of cancer.

Lung function tests. Also called pulmonary function tests (PFTs), lung function tests evaluate how much air the lungs can hold, how quickly air can move in and out of the lungs, and how well the lungs add oxygen and remove carbon dioxide from the blood.

X-ray. An x-ray is a picture of the inside of the body. An x-ray of the chest can sometimes help doctors determine the presence and location of mesothelioma, but is not the primary method of diagnosing mesothelioma.

Computed tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then puts these images into a detailed, cross-sectional view that shows abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein to provide better detail.

Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium (a special dye) may be injected into a patient’s vein to create a clearer picture.

Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. This substance gives off energy that is detected by a scanner, which produces the images.

To learn more about what to expect during common diagnostic tests, read Cancer.Net: Tests and Procedures.

To learn about the terms used in this section, read the Cancer.Net Feature: Cancer Terms to Know: Newly Diagnosed.