Mesothelioma TNM System

A patient diagnosed with mesothelioma will often learn about the stage, or level of development of the cancer. Most doctors "stage" the cancer when determining how far the disease has progressed. This staging step is often the most important piece of information a patient will learn that will greatly influence a prognosis and treatment plan. Doctors can gain important information by understanding how far the disease has progressed.

The field of cancer research and treatment has developed a variety of staging systems used to describe the progression and current state of a given disease. Most specific cancers have settled into using one particular method that is best suited for the tendencies and needs of that disease. In the world of mesothelioma, however, many subsets of the disease are very uncommon, making it difficult to heed the guidelines of just one system. The only form of mesothelioma that has been decisively staged is the most common form, or pleural mesothelioma. Doctors may apply staging principles to other forms of mesothelioma to facilitate conversation with the patient, but there are no hard and fast guidelines outside of the world of pleural mesothelioma.

To stage a tumor, most doctors begin by using an imaging procedure to uncover how far the cancer has spread. This may include taking a chest x-ray or employing a more high-tech scanning process such as a CT, MRI, or PET scan. Throughout this process, doctors are focusing on understanding the primary mass (or the extent of the main tumor), the extent to which the cancer has metastasized or spread, and whether or not lymph nodes have become involved. All major staging systems use a four-phased organization. In most cases, a diagnosis of Stage 3 or 4 is particularly serious. By this point, the patient may only be eligible for palliative treatments designed to relieve symptoms and improve quality of life.

Staging Mesothelioma with the TNM System

The TNM System (Tumor, Lymph nodes, and Metastasis) is a recently developed staging system that is sometimes used for malignant mesothelioma. The TNM System is also sometimes called the International Mesothelioma Interest Group staging system. Under the TNM System, malignant mesothelioma is categorized according to the size of the tumor, the level of metastasis, and the degree of lymph node involvement. The TNM System divides diseases into four numbered stages based on these criteria:

  • Stage I: Stage I is used to describe a cancer that appears on one side or the other of the pleura (or peritoneum, in the case of peritoneal mesothelioma). At this point, there is no lymph node involvement. If the disease being staged is pleural mesothelioma, the cancer may have metastasized to the pericardium, the lung, or the diaphragm (on the same side as the primary tumor only). If the disease being staged is peritoneal mesothelioma, the cancer has not metastasized to any other locations in the body. It remains relegated to one particular side of the peritoneum.
  • Stage II: Stage II is used to describe a situation in which cancer has spread from the primary tumor (generally the pleura of one lung) to lymph nodes on the same side of the body. In some cases, the designation of stage II may also be used to describe a cancer that has spread to the diaphragm, pericardial membrane, or the lung itself. The key, however, is that stage II under the TNM System relies on lymph node involvement.
  • Stage III: Stage III defines a disease in which the cancer has metastasized from the pleural membrane to the heart, ribs, esophagus, and other vital organs within the chest cavity. By stage III, lymph node involvement is almost certain.
  • Stage IV: Stage IV indicates a cancer that may be found on one or both sides of the body. The key factor, however, is that the cancer has likely spread to other organs beyond the initial site. The neck and lymph nodes are almost certainly involved.

Treating Mesothelioma

Many doctors base treatment decisions on the stage of the mesothelioma. A cancer that has been diagnosed as stage I or stage II, for example, may be operable, allowing a patient to undergo surgery to remove infected areas. Patients with stage III or stage IV cancer may render the patient eligible for palliative treatments only. Most doctors will recommend additional treatment such as chemotherapy and/or radiation to a patient to combat the disease.

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