Thymic Cancer Health Article

Definition

Thymic cancer is any one of several different types of tumors that have originated within the thymus gland.

Description

The thymus is located in the upper chest just below the neck. It is a small organ that produces certain white blood cells before birth and during childhood. These white blood cells are called lymphocytes and are an important part of the body's immune system. Once released from the thymus, lymphocytes travel to lymph nodes where they help to fight infections. The thymus gland becomes smaller in adulthood and is gradually taken over by fat tissue.

Three cell types of the thymus can give rise to cancer. The epithelial cells that make up the outer covering of the thymus can become cancerous resulting in thymic carcinoma and thymoma. When the lymphocytes in the thymus or lymph nodes become cancerous, the resulting cancers are called Hodgkin's disease or non-Hodgkin's lymphomas. A third, less common, cell type in the thymus is called Kulchitsky cells (neuroendocrine cells). These cells release chemical messengers called hormones. Cancer that originates from Kulchitsky cells is called thymic carcinoid tumors. Another type of thymic cancer, thymolipoma, is composed of thymic tissue and fatty tissue.

Although rare, thymomas are the most common type of thymic cancer. With fewer than 200 cases reported each, thymic cancer and thymic carcinoid tumors are very rare. Thymic carcinoma tends to spread and is more aggressive than thymoma.

Demographics

Thymic cancer is more common in the middle-aged and elderly. Thymoma and thymic carcinoma affect men and women equally. Thymic carcinoid tumors most frequently afflict men.

Causes and symptoms

The cause of thymic cancer is unknown. Cancer is caused when the normal mechanisms that control cell growth become disturbed, causing the cells to grow continually without stopping. This is caused by damage to the DNA in the cell.

Thymic tumors are not usually evident until the enlarged thymus presses on the windpipe (trachea) or blood vessels, which cause symptoms. The symptoms of thymic cancer will vary depending on what type of cancer is present. Symptoms of any thymic tumor may include: shortness of breath, swelling of the face, coughing, and chest pain.

Thymic carcinoid tumors can release hormones that may cause symptoms. Symptoms of thymic carcinoid tumors may also include red and warm skin, (flushing), diarrhea, and asthma.

Approximately 40% of the patients diagnosed with thymoma have no symptoms. The signs and symptoms of thymoma are vast and are related to the many disorders caused by thymoma. The most common conditions related to thymoma (paraneoplastic syndromes) are red cell aplasia, myasthenia gravis, and hypogammaglobulinemia. These conditions are autoimmune diseases, those in which the body mounts an attack against certain normal cells of the body. Symptoms of thymoma may also include:

• muscle weakness (especially in the eyes, neck, and chest, causing problems with vision, swallowing, and breathing)
• weakness
• dizziness
• shortness of breath
• fatigue

Diagnosis

The physician will conduct a complete physical exam. He or she may be able to feel a fullness in the lower neck region. Routine blood tests may be performed. Imaging studies are necessary because the symptoms of thymic cancer can be caused by many other diseases. Thymic tumors can be identified by chest x ray, magnetic resonance imaging (MRI), and computed tomography (CT).

A biopsy may be performed, in which a small sample of the tumor is removed and examined under the microscope. However, because of the risk of "seeding" cancerous cells, biopsies are not routinely performed. Because other tumors can lie in the region of the thymus, thymic cancer can be diagnosed only by identification of the cells that make up the tumor. There are a few different methods for biopsy of a thymic tumor. For a mediastinoscopy, a wand-like lighted camera (endoscope) and special instruments are passed through a small cut in the lower neck. The surgeon can see the tumor on a monitor and can cut off small samples for microscopic analysis. Mediastinoscopy is performed under general anesthesia. Alternatively, a needle biopsy will be taken in which a long needle is passed through the skin and into the tumor. Fine needle biopsy uses a thin needle and larger-core needle biopsy uses a wider needle. Needle biopsies may be performed in conjunction with computed tomography imaging.

Patients who are having difficulty breathing may have a bronchoscopy performed to examine the wind pipe. An endoscope, in this case a bronchoscope, is inserted through the mouth and into the windpipe. The physician will look for tumors and may perform biopsies.

Treatment team

The treatment team for thymic cancer may include a hematologist, pulmonologist, immunologist, oncologist, thoracic surgeon, cardiologist, radiation oncologist, nurse oncologist, psychiatrist, psychological counselor, and social worker.