From Biology-Online Dictionary | Biology-Online Dictionary


(Science: oncology, tumour) A tumour of thymic origin.

thymoma is a cancerous condition of the Thyamus gland. Located at the top of the heart, the thyamus gland contributes to the function of the immune system prior to puberty. At puberty, other organs take over the immune functions and the thyamus begins to be re-absorbed by the body, usually turning into fatty Tissue. In rare cases, the tissue of the thyamus becomes cancerous and a tumor begins to grow. These tumors are usually epithelial in nature although there are some variations (for more information see the WHO thymoma typing standards).

thymoma is different from other cancer types which is illistrated by it's behavior.

1. Thymoma cells do not change characteristics over the course of the


2. Thymoma does not spread through the lymph system like other cancers and

  therefore remains localized to the chest cavity.

3. Thymoma is staged differently than most other cancers using a scale called

  the Masoaka scale which is based on the amount of matastasis within the
  chest cavity.
           stage 1: Only one tumor located at the thyamus exists and it is
                    fully encapsulated or calcified.
           stage 2: The tumor is no longer encapsulated, but there are no
                    signs of matastasis.
           stage 3: tumor has begun to matastasize to other local organs and
                    structures like the outer lining of the lungs, aorta,
                    heart, or esophagus.
           stage 4a: thymoma cells have matastasized to more remote structures
                     in the chest cavity which may include but not be limited
                     to the hilum, paracardium, diaphram.
           stage 4b: Tumors have spread throughout the chest cavity and have
                     become invasive to the other organs.

Preferred treatment is surgical resection and is the most successful in stages 1 and 2. resection is still usually possible in stage 3, however the risk of recurrance is significantly higher. resection of stage 4 is usually referred to as "debulking" due to the fact that the odds of complete resection of all cancerous tissue is practically impossible without removing large sections of other organs which increases morbidity without decreasing the recurrance statistics.

treatment of stages 1-3 usually includes chemotherapy both neojunctive and adjunctive. Preferred substances are cisplatin and Etopiside given in combination. Other substances maybe substituted, but will be from the same family of chemo drugs. Both subcatagories of stage 4 will be treated almost exclusively with a chemotherapy regimen unless the oncologist and surgeon decide that debulking will either improve the quality of the patients life or significantly increase the patients longevity.

radiation treatment is an option, however due to the tumor's proximity to the heart and lungs, it may be considered too risky for more advanced cases. radiation will usually be given both neojuntively and adjunctively to resections of stage 1 and 2 tumors. application to stage 3 is usually at the radiology oncologist's discretion.

thymoma is usually grouped with another condition called Thymic carcinoma, mostly due to the fact that they are both cancerous conditions of the thyamus. however, they are distinctly different diseases with different cellular characteristics and different behaviors.

thymoma and thyamic carcinoma as a group are relatively rare. At the time of this writing they account for less than 2% of all cancers reported in the united states on an annual basis. As of this time there are no known causes of thymoma or Thyamic carcinoma. Links to any environmental, or hereditary characteristics have not been found and there are no known carcinogens that cause it's formation.