So Just what is the Thymus ?
The thymus sits in the front of the heart and plays a central role in the immune system. It uses blood stem cells to make T cells, which help the body fight infections and have the ability to eliminate cancer cells. However, as people age or become ill, the thymus isn’t as efficient at making T cells. T cells generated in the thymus acquire specialized molecules, called receptors, on their surface, and those receptors help T cells seek out and destroy virus-infected cells or cancer cells. To answer specifically, it is a small organ in the chest just above the heart and close to the breast bone. It is part of our lymphatic system. The role of the lymphatic system is to carry infection fighting white blood cells throughout the body to help fight off invaders like viruses and rid the body of toxins and cellular debris. This “flotsam and jetsam” circulates through the lymph vessels that run parallel to arteries and veins and have many, many filters along the way in the form of small bean sized organs called lymph nodes. There are approximately 600-700 of these lymph nodes throughout the body. In addition to acting as a filter, the lymph nodes produce and store infection fighting cells. The clear, colorless fluid called lymph passes through these filters where cells and debris are removed. While blood circulates in an “out and back” fashion sending blood from the heart to distant parts of the body and back, the lymph system runs in one direction only-from the feet and hands towards the neck where the lymph drains into the subclavian veins. Organs of the lymphatic system include the spleen, the thymus, the lymph nodes and the tonsils and adenoids.
Of course, we are most interested in the Thymus. This small organ is usually more active when we are young and plays a big role in the immune system. But as adults the thymus acts as a storage center to warehouse immature specialized white blood cells called lymphocytes. Its most important function is to prepare these immature cells to become active T-cells, or T lymphocytes. It is these fighter cells that battle infection and cancer (kind of ironic isn’t it?).
Types of Thymic Neoplasms (tumors)
The thymus gland itself is made up of two lobes. Its surface is lumpy due to its “lobules”. There are 3 basic layers or zones to the gland. There is a thin outer covering called the capsule. Then moving inward, there is the cortex or middle layer which surrounds the last layer or core of the gland, called the medulla. There are 3 cell types that make up these areas:
Epithelial cells which give the gland its structure and shape-it is these cells that give rise to thymic carcinoma and Thymoma. As noted above, the cortex is the site of rapid proliferation of the thymocytes, or thymic cells. This is why it is susceptible to developing cancer. The more cells are dividing and making new cells, the more likely they are to make a “mistake” when copying the information from one cell to the next. Lymphocytes which make up most of the organ-these are immune cells Kulchitsky cells-these are neuroendocrine cells that respond to hormonal influence .
Understand that Thymoma and Thymic carcinoma are epithelial tumors of the thymus gland (TET’s). In general, thymoma is less aggressive, more treatable and often associated with autoimmune disease, particularly Myasthenia Gravis. Thymic carcinoma, by contrast tends to be more aggressive, more difficult to treat and not associated with any autoimmune disease. There are 5 classes of Thymoma based on the type of cells present in the tumor. Thymic carcinomas are categorized as class C thymomas.
Tests that examine the thymus are used to detect (find) thymoma or thymic carcinoma.
The following tests and procedures may be used:
Physical exam and history : An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the chest, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body, such as the chest. This procedure is also called nuclear magnetic resonance imaging (NMRI).
PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
Thymoma and thymic carcinoma are usually diagnosed, staged, and treated during surgery.
A biopsy of the tumor is done to diagnose the disease. The biopsy may be done before or during surgery (a mediastinoscopy or mediastinotomy), using a thin needle to remove a sample of cells. This is called a fine-needle aspiration (FNA) biopsy. Sometimes a wide needle is used to remove a sample of cells and this is called a core biopsy. A pathologist will view the sample under a microscope to check for cancer. If thymoma or thymic carcinoma is diagnosed, the pathologist will determine the type of cancer cell in the tumor. There may be more than one type of cancer cell in a thymoma. The surgeon will decide if all or part of the tumor can be removed by surgery. In some cases, lymph nodes and other tissues may be removed as well.
