Thymic Neoplasms and Myasthenia Gravis

Overview
Diagnosis
Treatment

Thymic Neoplasms and Myasthenia Gravis Overview

Thymic neoplasms are tumors that develop in the thymus gland.

People with thymic neoplasms frequently have myasthenia gravis — a chronic, progressive autoimmune disorder that causes the muscles of the head, face, and body to become weak and easily fatigued.

About the thymus gland and thymic neoplasms

The thymus gland sits in the upper chest area just behind the breastbone (sternum). Its purpose is to make white blood cells (lymphocytes) that protect against infection.

Different types of tumors can develop in the thymus. Doctors refer to these as thymic neoplasms.

Types of thymic neoplasms:

Thymoma — the most common tumor of the thymus involving the cells on the outside surface of the thymus gland. Thymomas grow slowly and rarely spread (metastasize) to other parts of the body. The tumor cells in thymomas have a similar appearance to normal thymus gland cells. Thymomas are easier to treat than thymic carcinomas.
Thymic carcinoma — a rare type of thymic gland cancer with cells that look radically different from normal thymus gland cells. This type of thymic neoplasm grows more rapidly and frequently spreads to other parts of the body by the time a doctor discovers the cancer. Thymic carcinomas are more difficult to treat than thymomas.

People with thymic neoplasms frequently have an autoimmune disease — such as myasthenia gravis — that causes the body’s immune system to attack healthy tissues and organs.

About myasthenia gravis

Myasthenia gravis is a chronic and progressive autoimmune disease in which the cranial, facial, and body muscles become very weak and easily fatigued. It can occur in people of any age, but commonly occurs in women under 40 and men over 60.

Causes of myasthenia gravis

Myasthenia gravis is an autoimmune disorder that causes your body’s immune system to attack healthy organs and tissues in your body, resulting in their destruction.

Normally, your nerves send your muscles messages through a receptor. Nerves use a chemical called acetylcholine to deliver these messages. When the acetylcholine binds to the receptor area of a nerve, the muscle contracts.

With myasthenia gravis, the immune system attacks the muscle's receptor for acetylcholine.

Experts don’t understand exactly why the body begins to produce immune antibodies that attack the acetylcholine receptors. However, it seems to relate in some way to the thymus gland, which assists the body in producing antibodies.

Approximately 15 percent of those with myasthenia gravis also have a thymoma.

Contact Us

Contact the UPMC Esophageal and Lung Surgery Institute with questions or for more information.
Or, call the Thoracic and Foregut Surgery Division at 412-647-7555.

Thymic Neoplasms and Myasthenia Gravis Symptoms and Diagnosis

Symptoms of thymic neoplasms

Frequently, thymic neoplasms do not cause any recognizable symptoms. A doctor may discover the cancer during a routine chest x-ray.

If you experience any of the following symptoms, consult your doctor. A number of conditions could cause these symptoms and they aren’t necessarily indicative of thymic neoplasms.

Persistent, chronic cough
Chest pain
Difficulty breathing

Diagnosing thymic neoplasms

The health care team in UPMC's Division of Thoracic and Foregut Surgery may use one of the following tests or procedures to detect and identify a thymoma or thymic carcinoma:

Physical exam — your doctor will conduct a thorough exam to check for signs of disease or anything that appears unusual. He or she will likely take a history of your health habits, past illnesses, and treatments.
Chest x-ray — uses radiation to take pictures of the bones and organs inside your chest.
CT scan — uses a computer to take a series of detailed pictures of certain areas inside your body from several different angles. You may need to have dye injected into a vein or take it orally to make the organs and tissues inside show up more clearly.
Magnetic resonance imaging (MRI) — uses a powerful magnet, radio waves, and a computer to take a series of pictures of areas inside the body.
Positron emission tomography scan (PET scan) — requires that you have a small amount of radioactive glucose injected into your vein. The PET scanning device rotates around your body, taking pictures. Cancer cells show up as bright spots in the picture because they take up more glucose than normal cells do.

Symptoms of myasthenia gravis

The primary sign that a person may have myasthenia gravis is muscle weakness that diminishes upon resting.

Common symptoms include:

Drooping eyelids — one or both eyes
Double vision
Difficulty swallowing
Choking easily during eating
Difficulty chewing because of muscle fatigue
Fewer than normal facial expressions
Altered speech — soft or nasal sounding speech
Weakness in neck or arms

Diagnosing myasthenia gravis

Your doctor may conduct one or more tests to confirm a diagnosis of myasthenia gravis:

Edrophonium test — injection of the chemical edrophonium. If this results in a sudden, yet temporary, improvement in muscle strength and stamina, it’s a good indicator that you may have myasthenia gravis.
Blood panel — to check for certain abnormal antibodies.
Repetitive nerve stimulation — to test how muscles respond to nerve stimulation.
Single-fiber electromyography (EMG) — to check the health of the muscles and the nerves that control the muscles.
Imaging scans — CT scan or MRI to check for abnormal size or appearance of the thymus gland.

Contact Us

Contact the UPMC Esophageal and Lung Surgery Institute with questions or for more information.
Or, call the Thoracic and Foregut Surgery Division at 412-647-7555.

Thymic Neoplasms and Myasthenia Gravis Treatment

Thymectomy surgery for thymic tumors and myasthenia gravis

If you have a thymic tumor, with or without myasthenia gravis, you will need to undergo surgery — called a thymectomy — to remove your thymus gland. Even if you don’t have a thymic neoplasm, your doctor may advise you to undergo a thymectomy for myasthenia gravis.

Many health care facilities offer only open chest surgery for thymectomy procedures. Thoracic surgeons at the UPMC Esophageal and Lung Surgery Institute perform both minimally invasive and robotic-assisted thymectomies, in addition to traditional open chest surgery.

During a thymectomy, your surgeon will remove the affected part of the thymus or the entire thymus gland.

Even if the surgeon removes the entire thymic tumor or performs a thymectomy, he may also order radiation therapy after surgery to make sure no more cancer cells develop. This will lower your risk of the cancer returning.

Other adjuvant therapies for thymic neoplasms may include chemotherapy and hormone therapy.

Non-surgical interventions for myasthenia gravis

For mild cases of myasthenia gravis — or for people over 60 years of age — doctors can use the following non-surgical treatments to relieve symptoms:

Cholinesterase inhibitors
Corticosteroids
Immunosuppressants
Plasmapheresis
Intravenous immunoglobulin

Contact Us

Contact the UPMC Esophageal and Lung Surgery Institute with questions or for more information.
Or, call the Thoracic and Foregut Surgery Division at 412-647-7555.