Non-Small Cell Lung Cancer TNM Staging System
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Non-small cell lung cancer (NSCLC) staging is performed using the TNM system.
- Tumor (T) describes the size of the original tumor, and whether or not it has grown into nearby areas.
- Lymph Node (N) indicates whether the cancer is present in the regional lymph nodes. Cancer often spreads to the lymph nodes before entering other regions of the body.
- Metastasis (M) refers to whether cancer has spread to other parts of the body, usually the other lung, liver, adrenal glands, bones or brain.
A number (0-4) or the letter X is assigned to each factor. A higher number indicates increasing severity. For instance, a T1 score indicates a smaller tumor than a T2 score. The letter X means the information could not be assessed.
Once the T, N and M scores have been assigned, an overall stage is determined.
Primary Tumor (T)
The primary tumor can be categorized between the range of T0 up to T4 for lung cancer. Below is a further description of each stage used in the NSCLC TNM staging system.
TX: The main tumor cannot be assessed, or a tumor was identified due to the discovery of malignant cells in sputum (mucus coughed up from the lower airways), but no tumor was located.
T0: There is no evidence of a primary tumor.
Tis (carcinoma in situ): Cancer is only found in the top layers of cells lining the air passageways and has not spread.
T1: The tumor is less than 3 cm in overall size, has not reached the membranes surrounding the lungs and does not affect the main branches of the bronchi.
T1a: The tumor is smaller than 2 cm. T1b: The tumor is larger than 2 cm but smaller than 3 cm.
T2: The tumor has one or more of the following features:
- It is larger than 3 cm in size, but smaller than 7 cm (tumors between 3 cm and 5 cm are T2a, while those between 5 and 7 cm are T2b).
- The tumor invades a bronchus, but is located at least 2 cm from the carina, the cartilaginous ridged area that separates the opening of the right and left main bronchi stems.
- The tumor expands into the visceral pleura (the membrane that covers the surface of the lung).
- Part of the lung has collapsed or developed an inflammation/pneumonia, without involving the entire lung.
T3: The tumor has one or more of the following features:
- The tumor has expanded into the chest wall, the diaphragm, the membranes present in the space between the lungs or the membranes located in the sac surrounding the heart.
- The cancer has spread into the main bronchus and is within 2 cm of the carina, but does not actually affect the carina.
- The airways are blocked enough that the entire lung could collapse or become inflamed.
- Two or more separate tumors are present within the same lobe of one lung.
T4: The tumor has one or more of the following features:
- A tumor of any size has grown into the space between the lungs, the heart, any large blood vessels near the heart, the trachea, the esophagus, backbone or carina.
- Two or more separate tumors are present in different lobes of one lung.
Regional Lymph Nodes (N)
NX: Lymph nodes near the cancer cannot be assessed.
N0: The cancer has not spread into the lymph nodes.
N1: The cancer has spread to lymph nodes within the lung and/or the area where the bronchus enters the lung. The cancerous lymph nodes are located on the same side as the main tumor.
N2: The cancer has spread to lymph nodes around the carina or the space between the lungs (mediastinum). The affected lymph nodes are still on the same side as the main tumor.
N3: The cancer has spread to lymph nodes located near the collar bone on either side of the chest, and/or spread to the lymph nodes on the opposite side as the main tumor.
Distant Metastasis (M)
M0: The cancer has not metastasized.
M1a: The cancer has spread to the other lung, cancer is found in the fluid surrounding the lungs and/or cancer cells are identified in the fluid around the heart.
M2a: The cancer has spread to distant lymph nodes or other organs in the body, such as the kidney, adrenal gland, bones or brain.