Cancerous tumours are made up of millions of cells. Some of these cells may break away from the primary cancer and travel in the bloodstream or the lymphatic system to another part of the body - in this case, the lungs. Cancers that may spread to this area are those of the:
- large bowel (colon and rectum)
- gullet (oesophagus)
- kidney (renal)
- and a type of skin cancer called malignant melanoma.
Sarcomas (a type of cancer of the cells of the soft tissue of the body) can also spread to the lungs.
The symptoms of a secondary lung cancer may be distressing, and can include:
- a cough that doesn't clear up
- breathlessness coughing up bloodstained phlegm (sputum)
- persistent pain or discomfort in the chest.
Many of these symptoms are similar to those of a primary lung cancer. They are more commonly caused by conditions other than cancer, such as a chest infection, but you should see your doctor if you have any of these symptoms.
A doctor may suspect a secondary lung cancer if you've already been diagnosed with a cancer and you have some of these symptoms, particularly if they don't respond to other treatment such as antibiotics.
Sometimes, secondaries or metastases are found before a primary cancer has been diagnosed. Occasionally, it may not be possible to find the original cancer - this is called an 'unknown primary'.
*Information provided by Macmillan cancer support