If there is a reason to think you have a tumor of the thymus, your doctor will ask you about symptoms and use one or more exams or tests to find out if the disease is really present.

Symptoms of Thymic Cancers

Some thymic tumors are not noticed until they are large enough to press on nearby air passages or blood vessels. Pressure on the trachea (windpipe) causes shortness of breath. Pressure on veins that return blood from the head and neck to the heart can cause severe facial swelling. These symptoms are typically seen with thymic carcinomas (type C) and carcinoids.

Myasthenia gravis: About 30% to 50% of all thymomas are associated with myasthenia gravis. This is by far the most common autoimmune disease associated with thymomas. The body forms antibodies that block the receptors on the surface of muscle fibers that receive the chemical signals that stimulate the muscles to move. This causes severe muscle weakness. Indeed, myasthenia gravis is Latin for "severe muscle weakness," an accurate description of this disorder.

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 and problems with swallowing and breathing.

Although myasthenia gravis develops in around 30% to 50% of people with a thymoma, only 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). Medicines that reduce formation of anti-receptor antibodies, or strengthen the muscles to nerve signals are also used.

Red cell aplasia: Red cell aplasia, which means "lack of red blood cell formation," occurs in only 5% of thymoma patients. But 30% to 50% of people with red cell aplasia have a thymoma. Red blood cells are essential in carrying 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 include weakness, dizziness, shortness of breath, and reduced exercise tolerance. Red cell aplasia typically occurs in men and women older than 40 years of age. The treatment is to remove the thymus gland.

Hypogammaglobulinemia: Hypogammaglobulinemia is a disorder in which the body makes an abnormally low amount of normal infection-fighting antibodies, leaving the individual susceptible to infections. Hypogammaglobulinemia develops in 5% of thymoma patients. About 10% of patients with hypogammaglobulinemia have a thymoma. Unlike myasthenia gravis and red cell aplasia however, removing the thymus does not help correct this disease.

Several other conditions caused by immune system problems are also more common in people with thymomas than in the general population. However, they are much less common than myasthenia gravis, pure red cell aplasia, or hypogammaglobulinemia.

Other symptoms: While thymic carcinoids do not cause any of the paraneoplastic syndromes associated with thymomas, they sometimes cause a condition called the carcinoid syndrome. Certain hormones released by carcinoid tumors cause this 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. Thymic carcinoids can also cause symptoms by compressing veins or airways in the chest.

Medical History and Physical Examination

A complete medical history will reveal symptoms commonly associated with these tumors. However, most symptoms caused by thymomas are not specific and can be caused by other diseases as well. A physical exam will provide information about 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 more often diagnosed by recognizing the signs and symptoms associated with myasthenia gravis, hypogammaglobulinemia, and red cell aplasia.

Imaging Tests

Imaging tests use x-rays, magnetic fields, or radioactive substances to create pictures of the inside of your body. Several imaging tests are used to find thymoma and determine where it may have spread in the body.

Chest x-ray: This is the first test your doctor will order to look for thymoma. It is a plain x-ray of your chest and can be done in any outpatient setting. If the x-ray is normal, you still could have a small thymoma and your doctor may order additional tests.

Computed tomography (CT): The CT scan is an x-ray procedure that produces detailed cross-sectional images of your body. Instead of taking one picture, as does a conventional x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into an image of a slice of your body (think of a loaf of sliced bread). The machine will take pictures of many slices of the part of your body that is being studied. Often after the first set of pictures is taken you will receive an intravenous (IV) injection of a "dye" or radiocontrast agent that helps better outline structures in your body. A second set of pictures is then taken.

CT scans take longer than regular x-rays and you will need to lie still on a table while they are being done. You might feel a bit confined by the ring-like equipment you’re in when the pictures are being taken. But just like other computerized devices, they are getting faster and your stay might be pleasantly short. The newest CT scanners take only seconds to complete the study.

The contrast "dye" is injected through an IV line. Some people are allergic to the dye and get hives, a flushed feeling, or, rarely, more serious reactions like trouble breathing and low blood pressure. Be sure to tell your doctor if you have ever had a reaction to any contrast material used for x-rays. If you have, you may need medicine before you can have such an injection during your test.

You may also be asked to drink a contrast solution. This helps outline your intestine if your doctor is looking at organs in your abdomen to see if the thymoma has spread.

The CT scan will provide precise information about the size, shape, and position of a tumor, and can help find enlarged lymph nodes that might contain cancer. CT scans are more sensitive than a routine chest x-ray in finding thymomas. This test is also used to find masses in the adrenal glands, brain, and other internal organs that may be affected by the spread of thymoma.

Magnetic resonance imaging (MRI): 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 tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. Not only does this produce cross sectional slices of the body like a CT scanner, it can also produce slices that are parallel with the length of your body.

A contrast material might be injected just as with CT scans but is used less often. MRI scans take longer -- often up to an hour. Also, you have to be placed inside a tube-like piece of equipment, which is confining and can upset people with claustrophobia (a fear of enclosed spaces). The machine makes a thumping noise that you may find annoying. Some places will provide headphones with music to block this out. MRI images are particularly useful in detecting cancer that has spread to the brain or spinal cord.

Positron emission tomography: Positron emission tomography (PET) generally uses glucose (a form of sugar) that contains a radioactive atom. Other radioactive chemicals that tend to attach to thymoma cells can also be used. Cancer cells in the body absorb large amounts of the radioactive sugar and a special camera can detect the radioactivity. This may be useful in looking for spread of your thymoma. PET scans can be used instead of several different x-rays because they scan your whole body. Newer devices combine a CT scan and a PET scan to even better pinpoint the tumor.

Types of Biopsy Procedures

Although signs, symptoms, and imaging studies can suggest that a thymic tumor is likely to be present, doctors can’t be certain of the diagnosis without examining the tumor under a microscope. Normally for most cancers, a biopsy (sample of tumor tissue removed for examination under the microscope) 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 they might cause it to grow through the incision they make in the capsule. Because of this, doctors will either do the biopsy with a needle or operate to remove the tumor.

Needle biopsy: A long thin needle (about the same width as a needle used for blood tests) is used in a fine needle biopsy to remove small fragments of tissue. This is often not effective because thymomas are hard to diagnose. In order to get more tissue, doctors prefer a slightly wider needle. This core needle biopsy can remove a cylindrical piece of tissue that is larger (about 1/16 inch wide) than what can be obtained with a fine needle. The needle is inserted through the skin, and imaging procedures such as CT scans are used by the doctor to guide the needle into the correct location.

Many doctors prefer the needle biopsy when they suspect a thymoma. They are concerned that taking a bigger piece of the tumor may allow it to spread. If the person with the suspected thymoma has one of the "paraneoplastic" syndromes that were described, then the surgeon may operate without any biopsy, since the treatment (removal of the thymus) is the same, whether or not a thymoma is present. Last Revised: 11/10/2006