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. Each type of lung cancer also has its own set of stages. 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 80% of all lung cancers are non–small cell cancer.¹ It generally grows and spreads more slowly than small cell lung cancer.

• Adenocarcinoma. About 35% to 40% of lung cancers are adenocarcinoma.² 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.² 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.

Non–small cell lung cancer is classified into a number of different stages:

• Stage 0. Cancer at this stage is detected by chance during a bronchoscopy done for another reason.
• Stage I. Stages IA and IB are the most curable stages of lung cancer, but only about 15% of people with lung cancer are diagnosed at this stage. Treatment at this stage usually involves surgery to remove the cancer.
• Stage II. Stages IIA and IIB also are treated with surgery. Radiation therapy usually is not used after surgery at this stage. Chemotherapy that is done after surgery may increase long-term survival.³
• Stage III. Stage IIIA may be treated with chemotherapy, radiation, and surgery. Stage IIIB usually is treated with chemotherapy only or chemotherapy and radiation.
• Stage IV. Stage IV is advanced disease that has spread (metastasized) outside of the lungs and beyond the lymph nodes in the chest. It usually is treated with palliative chemotherapy.

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 smaller than 3cm. The cancer is only in the lung, and healthy tissue is found around it.
• T2. The tumor is larger than 3cm or involves the main airways (bronchi) or has spread to the lining (pleura) around the lung.
• T3. The tumor is of any size and has spread to:
  • The chest wall or the diaphragm below the lungs.
  • The area that separates the two lungs (mediastinum).
• T4. Cancer has spread to other organs in the chest, such as the heart, trachea, or esophagus.
• Recurrent. Cancer has come back (recurred) after it has been treated.

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 non–small cell 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 to another part of the body outside of the lungs.

The TNM staging system allows a health professional to recommend the most effective treatment options and 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.

Non–small cell lung cancer stages

Stage	TNM class
Occult	TXN0M0
0	TisN0M0
IA	T1N0M0
IB	T2N0M0
IIA	T1N1M0
IIB	T2N1M0 T3N0M0
IIIA	T1N2M0 T2N2M0 T3N1M0 T3N2M0
IIIB	Any T, N3M0 T4, any N, M0
IV	Any T, any N, M1

Small cell lung cancer

Small cell lung cancer is less common than non–small cell lung cancer. About 20% of lung cancers are small cell.¹ This type of cancer grows very rapidly and in more than 80% of people has already spread to other organs in the body by the time it is diagnosed.¹ Small cell lung cancer is more strongly related to smoking than non–small cell lung cancer.¹

The following stages are 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.

Citations

1. American Joint Committee on Cancer (2002). Lung. In AJCC Cancer Staging Manual, 6th ed., pp. 167–177. New York: Springer.

2. Chesnutt MS, et al. (2008). Pulmonary disorders. In SJ McPhee et al., eds., Current Medical Diagnosis and Treatment, 47th ed., pp. 203–243. New York: McGraw-Hill.

3. International Adjuvant Lung Cancer Trial Collaborative Group (2004). Cisplatin-based adjuvant chemotherapy in patients with completely resected non–small-cell lung cancer. New England Journal of Medicine, 350(4): 351–360.