The thymus is composed of two identical lobes and is located anatomically in the anterior superior mediastinum, in front of the heart and behind the sternum.
Histologically, the thymus can be divided into a central medulla and a peripheral cortex which is surrounded by an outer capsule. The cortex and medulla play different roles in the development of T-cells. Cells in the thymus can be divided into thymic stromal cells and cells of hematopoietic origin (derived from bone marrow resident hematopoietic stem cells). Developing T-cells are referred to as thymocytes and are of hematopoietic origin. Stromal cells include thymic cortical epithelial cells, thymic medullary epithelial cells, and dendritic cells.
The thymus provides an inductive environment for development of T-lymphocytes from hematopoietic progenitor cells. In addition, thymic stromal cells allow for the selection of a functional and self-tolerant T-cell repertoire. Therefore, one of the most important roles of the thymus is the induction of central tolerance.
The thymus is largest and most active during the neonatal and pre-adolescent periods. By the early teens, the thymus begins to atrophy and thymic stroma is replaced by adipose (fat) tissue. Nevertheless, residual T lymphopoiesis continues throughout adult life.
There are different types of tumors of the thymus. Thymoma and thymic carcinoma are tumors that affect the surface thymus. Thymoma tumors look almost like the normal tissue and does not spread beyond the thymus. The thymic tumor cells are very different from the thymus tissue and spread rapidly through the body.
Tumor cells in lymphoepithelioma-like thymic carcinoma have large, round, vesicular nuclei with prominent nucleoli. The tumor cells are positive for keratin and many cases contain EBV genome
Tumor cells in lymphoepithelioma-like thymic carcinoma have large, round, vesicular nuclei with prominent nucleoli. The tumor cells are positive for keratin and many cases contain EBV genome.
Possible signs of thymoma and thymic carcinoma include a cough and chest pain.Sometimes thymoma and thymic carcinoma do not cause symptoms. The cancer may be found during a routine chest x-ray. The following symptoms may be caused by thymoma, thymic carcinoma, or other conditions. A doctor should be consulted if any of the following problems occur:
- A cough that doesn't go away.
- Chest pain.
- Trouble breathing
The diagnosis is determined through chest x-rays, MRI scans and CT scans
Stages of Thymoma and Thymic CarcinomaTests done to detect thymoma or thymic carcinoma are also used to stage the disease.
Staging is the process used to find out if cancer has spread from the thymus to other parts of the body. The findings made during surgery and the results of tests and procedures are used to determine the stage of the disease. It is important to know the stage in order to plan treatment.
There are three ways that cancer spreads in the body.The three ways that cancer spreads in the body are:
- Through tissue. Cancer invades the surrounding normal tissue.
- Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
- Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.
For more info: