- What is lung cancer?
- Understanding your lungs
- Types of lung cancer
- What causes lung cancer?
- How common is lung cancer?
- Next steps
What is lung cancer?
Lung cancer is the result of damage to normal cells in the lung. Cancer that begins somewhere else in the body may spread to the lungs; this is different from lung cancer.
- Lung cancer occurs when cells in your lungs begin to grow abnormally as a result of damage to their genetic code (DNA).
- Cancer cells do not behave like normal cells — they grow abnormally and do not respond to signals to stop growing.
- Cancer cells also don’t organize normally. Instead they grow into a tumor, which may invade surrounding layers of tissue and spread to other organs.
- The cancer cells can enter your lymph system and begin to grow in lymph nodes around your bronchi and between your lungs (mediastinum).
- If lung cancer has reached your lymph nodes, it is more likely to have spread to other parts of your body, forming tumors (metastases) there.
Understanding your lungs
To understand lung cancer, it helps to know more about your lungs and lymph system.
Your lungs are sponge-like organs that work with your ribs, chest muscles and diaphragm muscle to move air in and out of your body, bringing in oxygen when you inhale and getting rid of carbon dioxide when you exhale.
- Air travels down your trachea, through your bronchi and bronchioles, into your alveoli and back out again.
- Your alveoli exchange carbon dioxide for oxygen through tiny blood vessels. The oxygen is carried to other parts of your body through your bloodstream.
Each lung has sections called lobes.
- Your right lung has three lobes and is slightly larger than your left.
- Your left lung has two lobes and is smaller because your heart takes up room on that side of your body.
Around your lungs are lymphatic vessels, small tubes that carry lymph away from your lungs.
- Lymph is clear fluid that carries waste products and immune system cells.
- In certain places along the lymphatic vessels you have lymph nodes — small, oval-shaped organs of the immune system.
- Lymphatic vessels link lymph nodes in the lungs to lymph nodes in the mediastinum.
Types of lung cancer
There are two main types of lung cancer:
- Non-small cell lung cancer, which accounts for about 85 percent of all lung cancers
- Small cell lung cancer, which makes up about 15 percent
Non-small cell lung cancer
Non-small cell lung cancer is classified into two main subtypes.
- Squamous cell carcinoma — which tends to be centrally located because it arises from the lining of your airways. Squamous cell carcinomas account for about 25 to 30 percent of all lung cancers.
- Nonsquamous non-small cell lung cancer — the most common type of lung cancer. This name covers a variety of cancers.
- The most common is adenocarcinoma, which begins in the glands that line your airways and is often found in an outer area of the lung.
- About 40 percent of lung cancers are adenocarcinomas. This is the most common type of lung cancer in non-smokers.
Small cell lung cancer
Small cell lung cancer occurs almost exclusively in heavy smokers. It usually starts in the bronchi, grows very quickly and creates large tumors. Most small cell lung cancers spread to sites outside the lung, such as the bones, liver or brain, before they are discovered.
Mesothelioma is an uncommon type of cancer related to the lungs. It arises from the pleura, the tissue that covers your lungs and lines your chest cavity, and is often linked to asbestos exposure.
Symptoms of lung cancer
Lung cancer symptoms may take years to develop, and often there are no symptoms at all until the later stages of the disease.
The early symptoms of lung cancer are often mistaken for less serious problems. Or, in people who smoke, they are thought to be related to tobacco use alone.
Early signs and symptoms of lung cancer
- Coughing — If you develop a new cough, you have a persistent cough that lasts more than two weeks or causes pain, or you cough up blood (a serious symptom), tell your doctor.
- Chest infection — Infections, like bronchitis or pneumonia, that don’t get better or recur, may be a lung cancer symptom.
- Trouble breathing — If you experience shortness of breath or wheezing, see your doctor to find out the reason.
- Chest discomfort — This could be a symptom of several different problems, including a heart or lung condition. If it’s persistent or sudden and severe, get medical attention immediately.
- Loss of appetite — Many illnesses, including cancer, cause changes in appetite. Keep track of this symptom and report it to your doctor if it persists.
- Weight loss — If you are losing weight for no known reason, let your doctor know.
- Fatigue — Excessive tiredness or weakness is common for many illnesses, including cancer.
Late signs and symptoms of lung cancer
- Neck and facial swelling
- Aching bones or joints or back pain
- Headaches and dizziness
- Lumps in the neck
- Pain, swelling or weakness in or around the chest or in distant parts of the body, which may indicate that cancer has spread
Conditions other than cancer may cause these symptoms. If you have any symptoms that concern you or if you are at high risk for developing lung cancer, talk to your doctor.
If you are or were a smoker and suspect you might have or might develop lung cancer, learn more about SCCA's low-dose CT screening program.
Diagnosing lung cancer
SCCA’s Lung Cancer Early Detection & Prevention Clinic is your gateway to getting a diagnosis if you’re suspected of having lung cancer or to reducing your risk if you’re lung cancer–free.
Sometimes lung cancer is detected before symptoms appear through a chest X-ray or other exam ordered for reasons not related to the cancer.
Your doctor may order imaging tests, such as an endobronchial ultrasound, a chest X-ray or a computed tomography (CT) scan to help diagnose lung cancer.
To confirm the diagnosis, you will need a biopsy. This involves taking a sample of tissue and looking at the cells under a microscope. A number of methods can be used.
- Bronchoscopy — A thin, lighted tube (bronchoscope) is inserted through your mouth or nose, down your windpipe and into your breathing passages so doctors can see inside and take a tissue sample.
- Endobronchial ultrasound–guided transbronchial needle aspiration (EBUS TBNA) — A special bronchoscope with an ultrasound processor is used to see the area between your lungs and take a tissue sample without any incisions.
- Needle biopsy — A needle is inserted through your chest wall into the tumor, usually under the guidance of CT imaging, to withdraw cells. This method might also be used to withdraw cells from tumors in other areas of your body, if you have any.
- Thoracentesis — A needle is used to remove fluid surrounding your lungs.
- Mediastinoscopy — A thin, lighted tube (mediastinoscope) is inserted through a small incision in your neck just above or next to your breastbone to see your lungs and surrounding lymph nodes and take a tissue sample.
- Thoracotomy — A surgeon opens your chest surgically to access the tumor.
If a biopsy confirms that cancer is present, your doctor will determine the type of cancer and the stage — how far the cancer has spread within your lungs or to other parts of your body.
Stages of lung cancer
Accurate staging is probably the most important part of lung cancer treatment because it helps your doctors choose the most appropriate therapy for you (and can help you avoid ineffective therapy).
How we determine the stage
The SCCA lung cancer team has a methodical and scientific approach to lung cancer staging that allows many patients to have more aggressive therapy with a goal of curing their disease, even when this may not have seemed possible based on initial X-ray evaluations.
X-rays can be misleading, so it is important to verify any X-ray findings that suggest you have more advanced cancer. Your cancer could be less advanced and your treatment options could be different than X-rays suggest.
To determine the stage of your disease:
- You may need scans, such as a CT scan, magnetic resonance imaging (MRI) scan, positron emission tomography (PET) scan, bone scan and brain scan.
- You may have a procedure called mediastinoscopy, in which a lighted scope is inserted through an incision in your neck to look at tissues in your chest.
- Your doctor may want to do biopsies of lymph nodes or suspicious areas seen on X-rays.
Non-small cell lung cancer stages
Non-small cell lung cancer is assigned an overall stage of I, II, III or IV, with stage I being the least advanced and stage IV being the most advanced. The stages may be further subdivided based on more precise features of the cancer.
Small cell lung cancer stages
Small cell lung cancer is staged as limited or extensive.
- Limited stage — The cancer is on one side of your chest and involves one region of your lung, your mediastinum (area between your lungs) and lymph nodes.
- Extensive stage — The cancer has spread outside your lungs to other parts of your body.
What causes lung cancer?
More than 85 percent of lung cancers are related to tobacco, either by smoking or breathing secondhand smoke, and about half of all continuing smokers will die from a disease caused by smoking.
Lung cancer due to smoking
Cigarette smoke contains more than 7,000 chemicals, many of them cancer-causing substances (carcinogens) that damage the cells in the lungs. At first your body may be able to repair the damage caused by the carcinogens, but with repeated exposure, the damage may progress to cancer.
The risk of lung cancer increases with the length of time and number of cigarettes you’ve smoked. Lung cancer occurs most frequently among people over 50 who have smoked for many years.
Heavy smokers are at the highest risk for lung cancer, but former smokers are also at risk. Nearly 60 percent of lung cancers are diagnosed in people who have already stopped smoking.
About 18 percent of people who develop lung cancer are lifetime never-smokers. As with many cancers, the cause is unknown. Secondhand smoke is thought to be responsible for about a quarter of cases of lung cancer in never-smokers.
Other lung cancer risk factors
Other risk factors for lung cancer include:
- Exposure to environmental carcinogens, including:
- Radon (a naturally occurring radioactive gas that results from the breakdown of uranium in soil and rocks)
- Chemicals or minerals, such as arsenic, beryllium, cadmium, chromium, nickel or silica
- Diesel exhaust
- Radiation exposure from occupational, medical or environmental sources
- History of lung cancer, Hodgkin or non-Hodgkin lymphoma or head or neck cancer
- History of emphysema, chronic obstructive lung disease or pulmonary fibrosis
- Family history of lung cancer
Tobacco use combined with one of these other risk factors can increase your lung cancer risk exponentially.
How common is lung cancer?
Lung cancer is the most common cancer after skin cancer, and it is the leading cause of cancer death for both men and women in the United States. Each year, more Americans die of lung cancer than of breast, colorectal, ovarian and prostate cancers combined.
About 222,000 new lung cancer cases are diagnosed in the U.S. each year.