There are three ways that cancer spreads in the body.
Cancer can spread through tissue, the lymph system, and the blood:
- Tissue. The cancer spreads from where it began by growing into nearby areas.
- Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
- Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.
Cancer may spread from where it began to other parts of the body.
When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.
- Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.
- Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.
The metastatic tumor is the same type of cancer as the primary tumor. For example, if non-small cell lung cancer spreads to the brain, the cancer cells in the brain are actually lung cancer cells. The disease is metastatic lung cancer, not brain cancer.
The following stages are used for non-small cell lung cancer:
Occult (hidden) stage
In the occult (hidden) stage, cancer cannot be seen by imaging or bronchoscopy. Cancer cells are found in sputum (mucus coughed up from the lungs) or bronchial washing (a sample of cells taken from inside the airways that lead to the lung). Cancer may have spread to other parts of the body.
Stage 0 (carcinoma in situ)
In stage 0, abnormal cells are found in the lining of the airways. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.
Stage I non-small cell lung cancer. In stage IA, cancer is in the lung only and is 3 cm or smaller. In stage IB, the cancer is (a) larger than 3 cm but not larger than 5 cm, (b) has spread to the main bronchus, and/or (c) has spread to the innermost layer of the lung lining. Part of the lung may have collapsed or become inflamed (not shown).