Types Of Lung Cancer
There are two main types of primary lung cancer, which behave and respond to treatment differently. They are:
- small cell lung cancer (SCLC)
- non-small cell lung cancer (NSCLC)
About 15% of lung cancers (less than 1 in 5) are small cell; the rest are non-small cell.
Small cell lung cancer
Small cell lung cancer is called this because when the cancer cells are looked at under a microscope they are very small. It’s sometimes called oat cell cancer.
Small cell lung cancer is usually caused by smoking, and it’s rare for someone who has never smoked to develop this type of lung cancer. Small cell lung cancer is often fast-growing and can spread quickly.
Non-small cell lung cancer
There are three main types of non-small cell lung cancer. Sometimes it’s not possible to tell which type someone has. This is because when the cells are looked at under a microscope, they are not developed enough or the biopsy doesn’t contain enough cells to diagnose the different types of NSCLC.
- Squamous cell carcinoma – This is the most common type of lung cancer. It develops in the cells that line the airways. This type of lung cancer is often caused by smoking.
- Adenocarcinoma – This develops from the cells that produce mucus in the lining of the airways. This type of cancer is becoming more common.
- Large cell carcinoma – This gets its name from the large, rounded cells that are seen when they are examined under a microscope. It’s sometimes known as undifferentiated carcinoma.
A less common type of cancer that can affect the covering of the lungs (the pleura) is called mesothelioma. This is a cancer of the membrane that covers the surface of the lungs and lines the inside of the chest. It often occurs in people who have been exposed to asbestos.
Rarer types of lung cancer
A rare type of cancer called a carcinoid tumor can sometimes develop in the lungs. Carcinoid tumors are a type of neuroendocrine cancer. The neuroendocrine system is a network of glands that produce hormones, which helps the different organs of the body to function. Rarer types of cancer, such as soft tissue sarcomas, can also develop in the lungs.
Secondary cancer in the lung (metastatic lung cancer)
Secondary cancer in the lung is when cancer cells have spread to the lungs from a cancer that began elsewhere in the body.
We hope this information answers your questions. If you have any further questions, you can ask your doctor or nurse at the hospital where you are having your treatment.
This information does not discuss primary lung cancer (cancer that started in the lung). We have separate information about primary lung cancer.
The lungs are a pair of organs in the chest that are responsible for breathing. When we breathe in, air passes from our nose or mouth, through the windpipe (trachea) and into two airways (bronchi), which enter the lungs. These airways divide to form smaller tubes, at the end of which are millions of tiny sacs.
It’s here that oxygen is absorbed from the air and passes into the bloodstream to be circulated around the body. The lungs are surrounded by a protective lining that consists of two membranes called the pleura.
Structure of the lungs and pleura
Cancer in the lung
Cancer can develop in the lungs in two ways. It can start in the lung (primary lung cancer), or it can spread there from a primary cancer elsewhere in the body. If a cancer spreads to the lungs from another part of the body, this is known as secondary or metastatic lung cancer.
Cancerous tumors 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 (esophagus)
- 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.
Signs and symptoms of secondary lung cancer
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'.
How secondary lung cancer is diagnosed
A number of tests may be done to diagnose a secondary lung cancer, including:
This may be taken to show the size and position of the cancer.
CT (computerized tomography) scan
A CT scan takes a series of x-rays that build up a three-dimensional picture of the inside of the body. The scan is painless and takes 10-15 minutes. CT scans use a small amount of radiation, which would be very unlikely to harm you or anyone you come into contact with. You'll be asked to not eat or drink for at least four hours before the scan.
You may be given a drink or injection of a dye, which allows particular areas to be seen more clearly. This may make you feel hot all over for a few minutes. It’s important to let your doctor know if you’re allergic to iodine or have asthma, because you could have a more serious reaction to the injection.
PET (positron emission tomography) scan
This uses low-dose radioactive sugar to measure the activity of cells in different parts of the body. A very small amount of a mildly radioactive substance is injected into a vein, usually in your arm. A scan is taken a couple of hours later. Areas of cancer are usually more active than surrounding tissue and show up on the scan.
Sometimes a biopsy may be needed. This is usually done in the x-ray department, most commonly during a CT scan. A local anesthetic is used to numb the area, then a needle is inserted to remove a small piece of tissue. The sample can then be examined under a microscope. The biopsy may be slightly uncomfortable but only takes a few minutes.
Secondary lung cancer may also cause fluid to collect in the space between the two membranes (the pleura) that surround the lungs. This is known as a pleural effusion. If this happens, it may be possible to remove some of the fluid and examine it for cancer cells.
When the cancer cells are examined, doctors can usually tell that it’s a secondary lung cancer because the cells look like the cells from the original cancer. For example, if a stomach cancer has spread to the lungs, the cells will look like stomach cancer cells rather than lung cancer cells.
Treatment for secondary lung cancer
The treatment for a secondary lung cancer depends on the individual situation, including your general health and the type of primary cancer. Sometimes a combination of treatments is used.
Chemotherapy is commonly given to reduce and control secondary cancers in the lung. The type of chemotherapy you have will depend on whether you've had chemotherapy before and how long ago.
Hormonal therapy is also commonly used to treat secondary cancers in the lung when they have developed from certain cancers, such as breast or prostate cancer, that are responsive to hormonal treatments. The type of hormonal therapy you have will depend on which hormonal treatments you've already been given.
Surgery to remove the secondary lung cancer may be possible for a small number of people. This may only be an option if the primary cancer has been controlled and there is no evidence of the cancer having spread anywhere else in the body. It also requires the cancer to be affecting just one small part of the lungs, which is easy to get to, and not attached to important blood vessels or nerves.
You might have a short course of radiotherapy to relieve some symptoms of secondary lung cancer, such as breathlessness or coughing up blood (haemoptysis).
If the cancer is causing a blockage in the windpipe or one of the large airways, laser therapy may be used to burn the tumor out of the airway. This may relieve some of the symptoms, though it does not destroy the cancer completely.
If the cancer is causing pressure on structures close to the windpipe, a small tube called a stent may be inserted to hold the windpipe open. The stent can remain in the lung permanently and does not generally cause any problems.
A special form of internal radiotherapy (brachytherapy) called endobronchial radiotherapy may be given when the tumor is blocking one of the airways. Using a flexible tube called a bronchoscope, a thin tube (catheter) containing radioactive material is placed close to the tumor. The radioactive material gives a dose of radiation to the tumor. It’s left in place for a few minutes to give the treatment and is then removed together with the catheter. Usually only one session of treatment is needed.
Coping with the symptoms of secondary lung cancer
The symptoms of a secondary lung cancer can affect a person's day-to-day life and can be distressing.
It can help to write down your main symptoms, so that you can discuss each one when you see your doctor.
This is a common and frightening problem that can affect all aspects of your life. The distress caused by being breathless can be partly relieved by medication and activities such as muscle relaxation. Your PCP can prescribe oxygen to ease your breathlessness. We have more information about managing breathlessness.
Fluid on the lung
A secondary lung cancer may cause a build-up of fluid between the two membranes (the pleura) that surround the lungs. This is known as a pleural effusion. The fluid puts pressure on the lung and may cause breathlessness, a cough and a dull, aching pain. These symptoms can be relieved by carefully draining the fluid through a tube. The tube is inserted into the chest in an area between the lower ribs. The doctor will inject a local anesthetic to numb the area before the tube is inserted. It is left in place for 2-3 days to drain.
Sometimes it isn't possible to drain the fluid as it can collect in a number of small pockets rather than in one place.
A pleural effusion can build up again, so a chemical may be inserted into the space between the pleura to try to prevent it from recurring. This procedure is called pleuradesis, and occasionally it may be done surgically under general anesthetic for better results. However, this is more complicated and will only be suitable for patients who are very fit.
Cough and chest pain
These can usually be relieved using medicines, which your doctor can prescribe.
Fear of choking
People who are experiencing problems with breathing may have a fear of choking. However, this is very unlikely to happen. If you are worried about this, discuss it with your doctor or nurse specialist. They can give you practical advice on what to do if you experience this feeling.
Coughing up blood (hemoptysis)
It's not unusual to notice some streaks of blood in your phlegm if you have secondary lung cancer. If you notice larger amounts of blood, let your doctor know so they can plan specific treatment (such as radiotherapy) to control it.
Research into treatments for secondary cancers in the lung is ongoing and advances are being made. Cancer specialists use clinical trials to assess new treatments. Before any trial takes place, an ethics committee must have approved it and agreed that the trial is in the interest of the patients.
You may be asked to take part in a clinical trial. Your doctor will discuss the treatment with you so you have a full understanding of the trial. You may decide not to take part, or withdraw from a trial, at any stage. You'll then receive the best standard treatment.