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Diagnosing mesothelioma is often difficult, because the symptoms are similar to those of a number of other conditions. Diagnosis begins with a review of the patient’s medical history, including any history of asbestos exposure. A complete physical examination may be performed, including x-rays of the chest or abdomen and lung function tests. A CT (or CAT) scan or an MRI may also be useful. A CT scan is a series of detailed pictures of areas inside the body created by a computer linked to an x-ray machine. In an MRI, a powerful magnet linked to a computer is used to make detailed pictures of areas inside the body. These pictures are viewed on a monitor and can also be printed.

A biopsy is needed to confirm a diagnosis of mesothelioma. In a biopsy, a surgeon or a medical oncologist (a doctor who specializes in diagnosing and treating cancer) removes a sample of tissue for examination under a microscope by a pathologist. A biopsy may be done in different ways, depending on where the abnormal area is located. If the cancer is in the chest, the doctor may perform a thoracoscopy. In this procedure, the doctor makes a small cut through the chest wall and puts a thin, lighted tube called a thoracoscope into the chest between two ribs. Thoracoscopy allows the doctor to look inside the chest and obtain tissue samples. If the cancer is in the abdomen, the doctor may perform a peritoneoscopy. To obtain tissue for examination, the doctor makes a small opening in the abdomen and inserts a special instrument called a peritoneoscope into the abdominal cavity. If these procedures do not yield enough tissue, more extensive diagnostic surgery may be necessary.

If the diagnosis is mesothelioma, the doctor will want to learn the stage (or extent) of the disease. Staging involves more tests in a careful attempt to find out whether the cancer has spread and, if so, to which parts of the body. Knowing the stage of the disease helps the doctor plan treatment.

Mesothelioma is described as localized if the cancer is found only on the membrane surface where it originated. It is classified as advanced if it has spread beyond the original membrane surface to other parts of the body, such as the lymph nodes, lungs, chest wall, or abdominal organs.

When to seek medical advice

See your doctor if you have signs and symptoms that may indicate mesothelioma. Signs and symptoms of mesothelioma aren't specific to this disease and may be related to other conditions. If any signs and symptoms seem unusual or bothersome to you, ask your doctor to check them out.

Screening and diagnosis

If you have signs and symptoms that might indicate mesothelioma, your doctor will conduct a physical exam, paying particular attention to areas where you're experiencing pain. He or she checks for any lumps or other unusual signs. Your doctor may order other tests to determine the cause of your signs and symptoms, including:

• Chest X-ray. X-rays may show abnormalities if you have pleural mesothelioma.
• Chest or abdominal CT scan. Computerized tomography (CT) may reveal abnormalities in your chest or abdomen if you have mesothelioma.

It's not uncommon for mesothelioma to be misdiagnosed initially because mesothelioma is rare and its signs and symptoms aren't specific. Your doctor will likely rule out other more common conditions before considering mesothelioma.

Biopsy
Biopsy, a surgical procedure to remove a small portion of the mesothelium for laboratory examination, is the only way to determine whether you have mesothelioma. Depending on what area of your body is affected, your doctor selects the right biopsy procedure for you. Options include:

• Fine-needle aspiration. The doctor removes fluid or a piece of tissue with a small needle inserted into your chest or abdomen.
• Thoracoscopy. Thoracoscopy allows the surgeon to see inside your chest. In this procedure, the surgeon makes one or more small incisions between your ribs. He or she inserts a tube with a tiny video camera to see inside your chest cavity — a procedure sometimes called video-assisted thoracoscopic surgery (VATS). Special surgical tools allow your surgeon to cut away a piece of tissue.
• Laparoscopy. Laparoscopy allows the surgeon to see inside your abdomen. Using one or more incisions into your abdomen, the surgeon inserts a tiny camera and special surgical tools to obtain a small piece of tissue for examination.
• Thoracotomy. Thoracotomy is surgery to open your chest to allow a surgeon to check for signs of disease. He or she removes a sample of tissue for testing.
• Laparotomy. Laparotomy is surgery to open your abdomen to allow a surgeon to check for signs of disease. He or she removes a sample of tissue for testing.

Once the tissue sample has been collected through biopsy, the sample is analyzed under a microscope. This determines whether or not the abnormal tissue is mesothelioma. Biopsy samples also allow your doctor to test for the type of cells involved in your mesothelioma. The type of mesothelioma you have is used to determine your treatment plan.

Staging
Once mesothelioma is diagnosed, your doctor orders other tests to determine the extent of the cancer and whether it has spread — a process called staging. Imaging procedures allow doctors to see inside your chest or abdomen to determine the stage of mesothelioma. Options include:

• Chest X-ray
• CT scans of the chest and abdomen
• Magnetic resonance imaging (MRI)
• Positron emission tomography (PET)

Once the extent of mesothelioma is determined, a stage is assigned. Staging helps your doctor determine your prognosis and the best treatment plan. The stages of mesothelioma are:

• I. Stage I mesothelioma is considered localized cancer, meaning it's limited to one small area of the chest or abdomen.
• II. Stage II mesothelioma is considered advanced cancer. Mesothelioma at this stage involves the mesothelium and has also spread to other structures directly adjacent to the tumor, such as the lungs or the diaphragm.
• III. Stage III mesothelioma is also considered advanced cancer. Mesothelioma at this stage meets the same requirements as stage II, but has also spread to the lymph nodes in the region.
• IV. Stage IV mesothelioma is an advanced cancer that has spread to distant areas (metastasized). Mesothelioma most commonly spreads (metastasizes) to the brain and areas of the lung that are away from the tumor.

Complications

As pleural mesothelioma spreads in the chest, it puts pressure on the structures in that area. This can cause complications, such as:

• Difficulty breathing
• Chest pain
• Difficulty swallowing
• Swelling caused by pressure on the large vein that leads from your upper body to your heart (superior vena cava syndrome)
• Pain caused by pressure on the nerves and spinal cord

Mesothelioma that progresses can lead to death. People who die of mesothelioma usually die from related complications, such as lung failure, bowel obstruction, heart problems, stroke and other causes.