Thymus Cancer

The thymus is a gland located in the upper part of the chest. It plays a significant role in the immune system of the body. The thymus plays an important role in the development of the immune system from prenatal to puberty. From about the twelfth week of gestation it grows until puberty. However, with the onset of public hormonal changes it begins to shrink.

Situated the upper anterior portion of the chest cavity the thymus is situated behind the breastbone (sternum) next to the lungs. the thymus has two lobes that join in front of the trachea. The two lobes are composed of lymphatic tissues which are tightly packed together. The tissues are fat, epithelium and lymphocytes.

The thymus releases hormones that stimulate the production of infection fighting T-cells. The lymphocytes become T cells when the body is infected with a virus. The T cells are an important part of the body's immune defenses against viruses. If the thymus does not develop normally in children it can contribute to immodeficiency disorders.

In earlier medical history the thymus was dismissed as an evolutionary relict like the appendix. It was viewed as merely a graveyard for lymphocyte cells. However, experiments conducted by Jacques Miller demonstrated the importance of the cells. He removed the thymus from three day old mice. These were later observed to be deficient in T cell production.

Lymphocytes from bone-marrow become thymocytes in the two thymic lobes. They eventually mature into T cells. After becoming T cells they leave the thymus can become the peripheral T cell reservoir. They are then able to direct many aspects of [Page 1663]the adaptive immune system. If the thymus is lost at an early age from injury, illness or genetic mal-mu-tation creates an immune deficiency condition that renders the body very susceptible to infections. The T cell receptor enables it to recognize antigens as foreign to the body.

During the T cell maturation process T cell receptor sites under go genetic organization that enables each to become specialized as unique receptors. This makes sets of T cells able to be able to have peptide (MHC) receptor site combinations. It also has the ability to recognize other T cells and to avoid treating them as antigens.

The thymic epithelial cells develop differently from the lymphoid thymocytes. They begin in the form of endodermal diverticula which are two flask-shaped pouches. As they eventually meet to grow together as connective tissue.

About ninety percent of thymic cancers are thymomas. The remaining types are thymic carcinomas, lymphomas, or carcinoid tumors. Occurrences of thymomas are rare. There are only about five hundred to seven hundred cases diagnosed in the United States each year. It is much more common is middle aged and the elderly regardless of gender.

Thymomas cancer is cancer of the thymic epithelial cells. Patients with myasthenia gravis have this from of cancer in from twenty-five to fifty percent of cases. Symptoms of thymomas cancer usually appear to be bronchitis because the tumor(s) presses against the cough nerve.

Thymomas tumors may grow in a range from slowly to rapidly. In some cases the thymomas is benign but these have the strong possibility of become cancerous. Those that grow rapidly may spread to surrounding tissue. Treatment of thymomas usually requires the removal of the thymus gland.

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