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Understanding the Stages of Thymus Cancer

Before deciding on treatment options, your doctor will need to know the extent of the thymus cancer, which is called the stage. Your doctor will look at the results of the tests you had in order to determine the stage of the cancer.

The stage of cancer tells how much and how far the cancer has spread. At this time, thymomas are the only type of thymus cancer that have a system of staging rules. Since thymic carcinoid tumors and thymic carcinomas are so rare, they do not have their own staging system.

The Masaoka staging system uses Roman numerals from I to IV (1 to 4) for the different stages:

Stage I. At this stage, the tumor is contained within the thymus gland.

Stage II. At this stage, the tumor has grown into or through the capsule surrounding the thymus gland into nearby fatty tissue or to the covering of the lungs called the pleura. Stage II cancer may also mean that a thymoma shows no spread on a surgical exam, but is beyond the thymus gland capsule when checked under a microscope by a pathologist.

Stage III. For this stage, the thymoma has grown into nearby tissues or organs in the lower neck or upper chest. These may include the covering of the heart, called the pericardium, the lungs, or the major blood vessels going in or out of the heart.

Stage IVA. For this stage, the thymoma has spread to multiple areas inside the chest, to the lining of the lungs, and/or to the pericardium.

Stage IVB. For this stage, the thymoma has spread through blood or lymph vessels to other organs, such as the liver or the kidneys.

Recurrent. Recurrent cancer means that the cancer has come back after it has been treated. It may come back in the thymus or in another part of the body.

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