Lung cancer is divided into two types, non-small-cell lung cancer and small-cell lung cancer. After the type of lung cancer is diagnosed, a doctor will assign patients with a stage. Staging cancer helps identify the extent of the cancer. Staging is a formal classification that aids doctors as to the proper treatment of each case. Staging is utilized solely to determine appropriate treatments, and does not indicate a prognosis. The two types of cancer are divided, meaning they have their own staging classifications.

Small-Cell Lung Cancer

Small-cell lung cancer is less complicated being divided into two stages: limited and extensive. The limited stage is just as the name indicates. At this stage the cancer is restricted to one lung with the possibility of cancerous cells in the lymph nodes of the chest cavity on the same side. Possible treatments usually include radiation or surgery due to the containment of cancerous cells. The extensive stage indicates that the cancer has metastasized, sometimes just to the other lung or possibly to lymph nodes of the opposite side, or other organs. Over half of those patients diagnosed with SCLC are diagnosed in the extensive stage.

Non-Small-Cell Lung Cancer

Non-small-cell lung cancer is a more intricate system with indicators for tumor, lymph node, and metastasis, which is expressed as the TNM system.

T- Indicates the size of the primary tumor and if it has grown into other areas.
N- Describes any spread of the cancer to nearby (regional) lymph nodes.
M- Notes if the cancer has metastasized to other organs.

The TNM system is coupled with an international staging system in order to better determine course of treatment and prognosis. Cancer stages increase in their severity, starting with stage IA on one side of the spectrum, and ending with stage IV.  Charted below the stages as they correlate to the TNM system:

  • Stage IA                                 T1N0M0
  • Stage IB                                 T2N0M0
  • Stage IIA                                T1N1M0
  • Stage IIB                                T2N1M0
  • Stage IIIA                               T1N2M0, T2N2M0, T3N1M0, T2N2M0
  • Stage IIIB                               Any T-T4, N3, M0 or T4, any N, M0
  • Stage IV                                 Any T, any N, M1

Along with stages and the TNM system, doctors assign numbers in order to further describe each component. The numbers zero through four signify progression, zero following the letter T, N, or M indicates no evidence of a tumor, node, or metastasis; the higher the number, the stronger the cancer’s progression. The presence of the letter X means that the primary tumor cannot be assessed. The following taxonomy better describe the tumor:

  • T1- The tumor is no larger than 3 cm across, and has yet to reach the visceral pleura, which are the membranes surrounding the lungs. This classification indicates that the main branches of the bronchi have not been affected.
  • T2- This number indicates that the tumor is between 3 cm and 7 cm across, has grown into the visceral pleura, and partially blocks the airways. The airway blockage has not yet caused a lung to collapse or development of pneumonia. A T2 involves a main bronchus, but is not closer than 2 cm to the carina, which is the point where the windpipe splits into the left and right main bronchi.
  • T3- This indicates a tumor that is larger than 7 cm across, and has occupied any of the following areas: the chest wall, diaphragm, mediastinal pleura (membranes surrounding the space between the lungs), parietal pericardium (the membranes of the sac that surrounds the heart), or the main bronchus. A T2 is closer than 2 cm to the carina but does not involve it. Growth into airways has lead either to a lung collapsing, or the cause of pneumonia in an entire lung. This classification can also indicate two or more separate tumor nodules present within the same lobe of a lung.
  • T4- A tumor of any size that has grown into either the mediastinum (the space between the lungs), the heart, large blood vessels near the heart, the windpipe, the esophagus, the backbone, or the carina. As with a T3, a T4 can also include the presence of two or more separate tumor nodules located in different lobes of the same lung.

The references mentioned for tumors: the numbers zero through four, as well as the use of the letter X, are used in the same manner for node classification:

  • N1- Lymph nodes within the lung and/or around the area where the bronchus enters the lung (known as hilar lymph nodes) have been affected. In the case of N1 the affected lymph nodes remain on the same side as the primary tumor.
  • N2- The cancer has spread to include the lymph nodes around the carina or the mediastinum. Affected lymph nodes remain on the same side as the primary tumor.
  • N3- This indicates that the cancer has spread to lymph nodes nearing the collarbone on either side, and/or spread to the hilar or mediastinal lymph nodes located on the opposite side of the primary tumor.

The final indicator for the TNM system is metastasis. This classification also mimics the format for tumor and lymph node, and is described below:

  • M0- The spread of cancer cannot be assessed, including to the other lung, lymph nodes beyond those mentioned in the N stages, and organs or tissues such as the liver, brain, or bones.
  • M1a- Involves metastasis that includes any of the following: the cancer has spread to the other lung. Cancer cells have been found in the fluid around the lung (known as a malignant pleural effusion), or in the fluid around the heart (known as a malignant pericardial effusion).
  • M1b- Indicates that the cancer has spread to distant lymph nodes or other organs such as the bones, brain, or liver.

Early detection remains an important factor in lung cancer, especially as it pertains to diagnosis, staging, and treatment. Those who have been exposed to asbestos are prone to lung-related illnesses such as asbestosis. Prolonged exposure like that exhibited in factory workers, miners, and similar industries remain among leading causes for cancers such as mesothelioma and lung cancer. Because of the long latency period of both, first symptoms may not present until decades after the exposure. Early detection is a key element for patients with these diseases. A consultation with a licensed physician or specialist is the only way to insure a proper diagnosis.


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