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.