If there is a reason to think you may have a tumor of thethymus, your doctor will ask you about symptoms and use one or more exams or tests to find out if the disease is really present. Certain signs and symptoms might suggest that a person may have a thymus tumor, but tests are needed to confirm the diagnosis.

Signs and symptoms of thymus cancers

Most thymic tumors are brought to the attention of a doctor after a person starts to have symptoms. These may be related to the tumor itself, or they may be part of a paraneoplastic syndrome.

Symptoms caused by the tumor

The thymus is in the middle of the chest, near the airways and certain blood vessels. Tumors in the thymus can result in symptoms such as:

• shortness of breath
• cough (which may be bloody)
• chest pain
• trouble swallowing
• loss of appetite
• weight loss
• fever

The thymus is near the superior vena cava, the main blood vessel bringing blood from the head and upper body to the heart. Tumors that press on this vessel can cause symptoms of superior vena cava syndrome, which can include:

• swelling in the face, neck, and upper chest, sometimes with a bluish color
• swelling of the visible veins in this part of the body
• headaches
• feeling dizzy or light-headed

Paraneoplastic syndromes

These are conditions that are related to the cancer but that are not caused directly by the tumor mass. For example, people with thymomas may develop autoimmune diseases, where the immune system starts to attack the body itself. Part of the normal function of the thymus is to help keep the immune system in check, which may help explain why this happens.

Myasthenia gravis: About 30% to 50% of people with thymomas also have myasthenia gravis. This is by far the most common autoimmune disease associated with thymomas. In this disease, the immune system forms antibodies that block the chemical signals that stimulate the muscles to move. This causes severe muscle weakness.

Patients have decreased muscle strength throughout the body, but most severely involved are the muscles of the eyes, neck, and chest, causing blurred or double vision, drooping eyelids, and problems with swallowing and breathing.

While many people with thymomas also have myasthenia gravis, only about 15% of patients diagnosed with myasthenia gravis have thymomas. An additional 55% of people with the disorder have other, noncancerous abnormalities of the thymus gland. Myasthenia gravis can be treated by removing the thymus (whether or not a thymoma is present) or with medicines that either strengthen the chemical signals to muscles or weaken the immune attack on the muscles.

Red cell aplasia: Red cell aplasia, in which the body's ability to make new red blood cells is severely reduced, occurs in about 5% of thymoma patients. Red blood cells carry oxygen from the lungs to other tissues of the body. Reduced red blood cell production causes anemia (low red blood cell counts). Symptoms of anemia can include weakness, dizziness, shortness of breath, and tiring easily. The usual treatment is to remove the thymus gland.

Hypogammaglobulinemia: Hypogammaglobulinemia is a disorder in which the body makes low amounts of infection-fighting antibodies (also known as gamma globulins). This leaves the person susceptible to infections. Hypogammaglobulinemia develops in about 5% to 10% of thymoma patients. About 10% of patients with hypogammaglobulinemia have a thymoma. Unlike myasthenia gravis and red cell aplasia, removing the thymus does not help correct this disease.

Other autoimmune diseases: Several other conditions caused by immune system problems are also more common in people with thymomas. However, they are much less common than myasthenia gravis, pure red cell aplasia, or hypogammaglobulinemia. Some examples include:

• systemic lupus erythematosus
• polymyositis
• ulcerative colitis
• rheumatoid arthritis
• Sjogren syndrome
• sarcoidosis
• scleroderma

Most people who have these autoimmune diseases do not have a thymoma.

Carcinoid syndrome: While thymic carcinoids do not cause any of the paraneoplastic syndromes associated with thymomas, they sometimes release hormones that cause a condition called the carcinoid syndrome. Symptoms include flushing (redness and warmth of the skin due to increased blood flow), diarrhea, and asthma. Most people with carcinoid syndrome do not have all of these symptoms, and most thymic carcinoids do not cause the carcinoid syndrome.

Although the symptoms and signs above may be caused by thymus tumors, they may also be caused by other conditions. Still, if you have any of these problems, it's important to see your doctor right away so the cause can be found and treated, if needed.

Medical history and physical exam

If you have any signs or symptoms that suggest you might have a thymus tumor, your doctor will want to take a complete medical history to check for symptoms. You will also be asked about your general health.

A physical exam provides information about possible signs of thymic cancer and other health problems. Patients with thymic cancer will sometimes have a fullness that the doctor can feel in the lower neck area.

Thymomas are often diagnosed by recognizing the signs and symptoms associated with myasthenia gravis, hypogammaglobulinemia, or red cell aplasia.

If symptoms and/or the results of the physical exam suggest a thymus tumor might be present, more involved tests will likely be done. These might include imaging tests, lab tests, and other procedures.

Imaging tests

Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Imaging tests may be done for a number of reasons, including to help find a suspicious area that might be cancerous, to learn how far cancer may have spread, and to help determine if treatment has been effective.

Chest x-ray

A chest x-ray may be the first imaging test that a doctor orders if he or she suspects a problem in the middle of the chest. It may be able to show if there is a tumor in the chest. In fact, in some cases it may find tumors in people who aren't having any symptoms or are having the x-ray done for another reason. However, some thymomas that are small or are in certain places may not show up on a chest x-ray. If your doctor is still suspicious or if a vague abnormality appears on the chest x-ray, a CT scan may be ordered.

Computed tomography (CT) scan

The CT scan is an x-ray procedure that produces detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you are lying on a narrow platform. A computer then combines these into images of slices of the part of your body that is being studied. Before the scan, you may be asked to drink a contrast solution and/or get an intravenous (IV) injection of a contrast dye that helps better outline abnormal areas in the body.

You may need an IV line through which the contrast dye is injected. The injection can cause some flushing (redness and warm feeling). Some people are allergic and get hives or, rarely, more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays.

You need to lie still on a table while the scan is being done. During the test, the table moves in and out of the scanner, a ring-shaped machine that completely surrounds the table. You might feel a bit confined by the ring you have to lie in while the pictures are being taken.

In recent years, spiral CT (also known as helical CT) has become available in many medical centers. This type of CT scan uses a faster machine. The scanner part of the machine rotates around the body continuously, allowing doctors to collect the images much more quickly than standard CT. As a result, you do not have to hold your breath for as long while the image is taken. This lowers the chance of blurred images occurring as a result of breathing motion. It also lowers the dose of radiation received during the test. The slices it images are thinner, which yields more detailed pictures.

CT scans can have several uses:

• CT scans of the chest can spot very small tumors and help determine the exact location and extent of the tumors.

• CT scans can be helpful in staging a cancer (determining the extent of its spread). For example, they can show whether the cancer has spread to nearby lymph nodes or to the liver, kidneys, brain, or other organs.

• CT scans can also be used to guide a biopsy needle precisely into a suspected tumor or metastasis. For this procedure, called a CT-guided needle biopsy, the patient remains on the CT scanning table while a radiologist advances a biopsy needle through the skin and toward the location of the mass. CT scans are repeated until the needle is within the mass. A biopsy sample is then removed and looked at under a microscope.

• During or after treatment, CT scans may be used to see whether tumors are shrinking or have recurred (come back) in other parts of the body.

Magnetic resonance imaging (MRI) scan

Like CT scans, MRI scans provide detailed images of soft tissues in the body. But MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into very detailed images of parts of the body. A contrast material called gadolinium is often injected into a vein before the scan to better see details.

MRI scans may be a little more uncomfortable than CT scans. They take longer -- often up to an hour. You may be placed inside a large cylindrical tube, which is confining and can upset people with a fear of enclosed spaces. Newer, more open MRI machines can help with this if needed. The MRI machine makes buzzing and clicking noises that you may find disturbing. Some places will provide earplugs to help block this out.

MRI images are particularly useful in looking for cancer that may have spread to the brain or spinal cord.

Positron emission tomography (PET) scan

For a PET scan, you receive an injection of a substance that contains a radioactive atom. This is usually glucose (a type of sugar), but other substances that are attracted to thymoma cells may also be used. The amount of radioactivity is very low. The cancer cells in the body absorb large amounts of the radioactive substance. A special camera can then be used to create a picture of areas of radioactivity in the body. The picture is not finely detailed like a CT or MRI scan, but it can provide helpful information about your whole body.

A PET scan can help give the doctor a better idea of whether an abnormal area seen on another imaging test is a tumor or not. If you have already been diagnosed with cancer, your doctor may use this test to see if the cancer has spread to lymph nodes or other parts of the body. A PET scan can also be useful if your doctor thinks the cancer may have spread but doesn't know where.

Some newer machines are able to perform both a PET and CT scan at the same time (PET/CT scan). This allows the doctor to compare areas of higher radioactivity on the PET scan with the more detailed appearance of that area on the CT.

Blood tests

Blood tests can't be used to diagnose thymomas directly, but they may still be helpful in some situations. For example, tests may be done to look for certain antibodies in the blood of people who may have myasthenia gravis or other autoimmune disorders. Other blood tests may be done to make sure a mass in the middle of the chest isn't a germ cell tumor or part of the thyroid gland.

If a thymoma is diagnosed, blood cell counts and blood chemistry tests are done to get an idea of a person's overall health, especially if surgery is planned. Blood tests are also done regularly in people getting chemotherapy to make sure the drugs aren't having unwanted effects on the bone marrow, kidneys, or other organs.

Types of biopsy procedures

Although signs, symptoms, and imaging tests can suggest that a thymic tumor is likely to be present, doctors can't be certain of the diagnosis without looking at the tumor under a microscope.

For most cancers, removal of a small sample of the tumor (known as a biopsy) is needed to confirm whether a tumor is present and, if so, to determine its type. This is difficult for thymomas. Doctors are reluctant to cut into the tumor for a biopsy for fear that it might allow it to grow through the incision they make in the capsule around the thymus. Because of this, doctors usually either do the biopsy with a needle or operate to remove the entire tumor.

Needle biopsy

Suspected tumors in the chest are sometimes sampled by needle biopsy. A long, hollow needle is passed through the skin in the chest. Imaging tests such as CT scans are used to guide the needle into the tumor so that a small sample can be removed to be looked at under the microscope. This procedure is done without a surgical incision or overnight hospital stay.

Many doctors prefer to do a needle biopsy when they suspect a thymoma. They are concerned that taking a bigger piece of the tumor may allow it to spread. A possible downside of this test is that it may not always provide enough of a sample to make an accurate diagnosis or allow the doctor to get a good sense of the extent of the tumor.

"Biopsy" during surgery

In some cases if the doctor believes there is a good chance that a person has a removable thymoma (for example, he has a paraneoplastic syndrome and a small, well-defined mass in the chest), then the doctor may operate without any biopsy. This can both provide enough of a sample for a diagnosis and treat the tumor at the same time. The specimen is sent to the lab after surgery to confirm the diagnosis. See the section "Surgery" for more information.

Last Medical Review: 05/18/2009
Last Revised: 05/18/2009