Types and Stages of Lung Cancer

There are two main types of lung cancer: non–small cell lung cancer and small cell lung cancer. Each looks different under a microscope and grows and spreads differently. But both types of lung cancer share the same staging system. Your doctor will consider the type and the stage of lung cancer in determining the possible options for treatment.

Non–small cell lung cancer

Non–small cell lung cancer is more common than small cell lung cancer. About 85% of all lung cancers are non–small cell cancer. It generally grows and spreads more slowly than small cell lung cancer.

• Adenocarcinoma. About 35% to 40% of lung cancers are adenocarcinoma.¹ This type often begins near the outside surface of the lung and may vary both in size and how fast it grows. Adenocarcinoma is likely to spread to lymph nodes and other organs. This type is more common than other types of lung cancer in women, nonsmokers, and former smokers.
• Squamous cell carcinoma, also called epidermoid carcinoma. About 25% to 35% of all lung cancers are squamous cell.¹ This type usually begins in one of the larger airway tubes (bronchi), generally grows more slowly than the other types of non–small cell cancer, and may vary in size from very small to very large. Squamous cell carcinoma may spread to nearby lymph nodes or to other organs.
• Large cell carcinoma. About 5% to 10% of all lung cancers are large cell.² This type often begins near the surface of the lung and usually is large when diagnosed. Large cell carcinoma is likely to spread to lymph nodes and other organs.

Small cell lung cancer

Small cell lung cancer is less common than non–small cell lung cancer. About 15% of lung cancers are small cell. This type of cancer grows very rapidly and in most people has already spread to other organs in the body by the time it is diagnosed.

The following stages may be used for small cell lung cancer:

• Limited stage. Cancer is found only in one lung and in nearby lymph nodes.
• Extensive stage. Cancer has spread (metastasized) outside the lung to other tissues in the chest or to other parts of the body. This includes having a malignant pleural effusion.
• Recurrent stage. Recurrent disease means that the cancer has come back (recurred) after it has been treated. It may come back in the lungs or in another part of the body. Recurrent small cell lung cancer has a poor outcome, with most people living only 2 to 3 months after recurrence. A cancerous (malignant) pleural effusion is considered extensive stage in small cell lung cancer.

Lung cancer staging

Both non–small cell lung cancer and small cell lung cancer may be classified into a number of different stages, from Stage 0 to Stage IV.

This staging system is further defined by the extent of the tumor, lymph node involvement, and metastasis (TNM). The primary tumor (T) is staged in the following way:

• T0. No primary tumor is seen.
• TX. Cancer cells are found in sputum (mucus), but no tumor is found in the lung.
• Tis (Tumor in situ). This type of lung cancer is called carcinoma in situ. This means that the cancer is found in only one area of the lung and only in a few layers of cells. It has not grown through the top lining of the lung.
• T1. The primary tumor is 3 cm (1.18 in.) or less. The cancer is only in the lung, and healthy tissue is found around it.
  • T1a. The tumor is 2 cm (1 in.) or less.
  • T1b. The tumor is more than 2 cm (1 in.) but not more than 3 cm (1 in.).
• T2. The tumor is larger than 3 cm (1.18 in.) but not more than 7 cm (3 in.). Or it involves the main airways (bronchi) or has spread to the lining (pleura) around the lung.
  • T2a. The tumor is larger than 3 cm (1 in.) but not more than 5 cm (2 in.).
  • T2b. The tumor is larger than 5 cm (2 in.) but not more than 7 cm (3 in.).
• T3. The tumor is larger than 7 cm (3 in.), the tumor is in the main bronchus, or the cancer has spread to:
  • The chest wall or the diaphragm below the lungs.
  • The area that separates the two lungs (mediastinum).
  • A separate tumor in the same lobe.
• T4. The tumor is of any size, and the cancer has spread to other organs in the chest, such as the heart, trachea, or esophagus. Or the tumor has spread to another lobe on the same side of the chest.

After the tumor (T) is staged, the TNM system stages lymph node involvement (N) to help determine the treatment options at each stage. Lymph node involvement is staged in the following way:

• N0. No lymph node involvement.
• N1. Cancer has spread to nearby lymph nodes.
• N2. Cancer has spread to lymph nodes in the mediastinum.
• N3. Cancer has spread to lymph nodes on the other side of the chest from the primary tumor or into the neck near the trachea.

The last part of staging lung cancer is to determine whether cancer has spread (metastasized) to other parts of the body. The TNM system stages metastasis (M) in the following way:

• M0. No metastasis.
• M1. Cancer has spread outside the lung in which it started.
  • M1a. The cancer has spread to the opposite lung or there is an abnormal amount of fluid with cancer cells, either in the lining of the lungs (malignant pleural effusion) or the heart (pericardial effusion).
  • M1b. The cancer has spread outside the lungs to other parts of the body.

The TNM staging system allows a doctor to recommend the most effective treatment options and to discuss the long-term outcome (prognosis) based on the type of tumor, the stage of the cancer, and the person's age and overall health.

The stage and TNM class are grouped in the following table.³