Lung Cancer


Lung cancer is the second most common cancer in both men and women, behind prostate cancer for men and breast cancer for women. To better understand how the disease affects your lungs, it helps to have a basic understanding of cancer.

Cancer begins in cells, the building blocks of tissue in the body. Abnormal cells begin to grow out of control, and these cells grow more quickly, live longer than normal cells and don’t die when they get old or damaged. Over time, the cells form a mass known as a primary tumor.

Lung cancer starts in the epithelial cells in the lungs, which are the cells that line the airways (see Figure 1). If left untreated, the primary tumor in the lung can grow and invade the tissue surrounding the lung (the pleura). The cancer cells can replace so many normal cells that they make it difficult for the person to breathe. Sometimes cancer cells break off from the primary tumor and form secondary tumors in nearby sites, such as another lobe of the lung, or distant sites, such as the brain. Over time, new tumors form. This spread of cancer is called metastasis. When metastasis occurs, the cancer found in the new region is still considered lung cancer and is treated as such.

Cancer cells spread through blood or lymph vessels in the lungs. Lymph vessels collect and carry clear fluid (lymph) to lymph nodes, small disease-fighting organs that destroy the germs picked up by lymph. Lymph vessels and nodes are found all over the body. Lung cancer often spreads first to lymph nodes in the lungs and then to lymph nodes between the lungs in the area called the mediastinum.

How lung cancer develops

Lung cancer is the uncontrolled growth of abnormal cells lining the airways (bronchi) of the lung (Figure 1). Researchers believe lung cancer develops slowly over the course of many years after exposure to cancer-causing substances (carcinogens), resulting in more and more genetic abnormalities that accumulate in the cells. Over time, the abnormal cells become malignant (cancerous), divide and spread.

The overwhelming cause of lung cancer is the use of tobacco products such as cigarettes, pipes or cigars. The earlier in life a person starts smoking, the more packs of cigarettes a person smokes, and the more years a person smokes, the greater the chance for lung cancer. Once a person stops smoking, the risk becomes lower each year, but the risk is still higher than for people who have never smoked.

As many as one in five lung cancers develop in people who have never smoked, most often women. In some of these cases, unknown factors are responsible. Exposure to secondhand smoke, asbestos and radon also increase the threat of lung cancer, and family history and ethnicity are other factors as well.

Even though lung cancer grows slowly, it spreads through the bloodstream and is difficult to detect early, primarily because there are no early symptoms of lung cancer. In addition, many of the first symptoms, such as a cough, are also symptoms of chronic lung disease caused by tobacco products. This means there’s nothing to alert a person to seek medical care.

However, a method to screen for lung cancer – low-dose spiral computerized tomography (CT) – now exists and is recommended for people at high risk for lung cancer. A person is at high risk if he or she is 55 to 74 years old, has smoked the equivalent of a pack of cigarettes daily for 30 or more years, and has stopped smoking fewer than 15 years previously. A large study showed that among a group of high-risk people, fewer people died of lung cancer when they were screened with low-dose spiral CT compared with people who were screened with standard chest X-rays. The International Association for the Study of Lung Cancer (IASLC) and other organizations suggest that high-risk individuals should discuss a screening CT scan with their doctor.

Figure 1. Anatomy of the Lungs

The lungs are spongy, air-filled organs located on either side of the chest (thorax). The right lung has three lobes, and the left lung has two lobes. Air enters the lungs through the nose and mouth, moving through the windpipe (trachea) and into the airways (bronchi) in the lung. Those airwaves divide into smaller branches, called bronchioles, and end in microscopic air sacs (alveoli), where oxygen and carbon dioxide are exchanged.

The lungs are covered by a thin layer of tissue called the visceral pleura. Another layer of this same kind of tissue lines the inside of the chest cavity. This layer is called the parietal pleura. Fluid between these two tissue layers acts as a lubricant as the lungs expand and contract during breathing. The diaphragm is a muscle at the base of the lungs that helps in breathing.

Types of Lung Cancer

Lung cancer is often defined by pathologists as adenocarcinoma, squamous cell lung cancer, large cell lung cancer or small cell lung cancer based on the features of the cancer cells in a biopsy fluid sample. Adenocarcinoma, squamous cell and large cell carcinoma are sometimes collectively referred to as non-small cell lung cancer and account for the majority of lung cancer diagnoses. Each has different characteristics and different responses to treatment. It is important for doctors to distinguish between lung cancer that begins in the squamous cells from lung cancer that begins in other cells as treatment decisions can be based on this information.

Adenocarcinoma starts in early versions of the cells that would normally secrete substances such as mucus and are usually found in the outer parts of the lung. This type is the most common lung cancer diagnosed in nonsmokers. It is more common in women than in men and is the most common type of lung cancer in younger people. In general, adenocarcinoma tends to grow more slowly than other types of lung cancer and is slightly more likely to be found before it has spread.

Squamous cell lung cancer starts in early versions of squamous cells, which are flat cells that line the inside of the airways in the lungs. It is often linked to a history of smoking and tends to be found in the central part of the lungs, near the main airway (bronchus).

Large cell lung cancer can develop in any part of the lung and tends to grow and spread quickly.

Small cell lung cancer is named for the size of the cancer cells when seen under a microscope. This type of cancer often starts in the bronchi near the center of the chest and almost always spreads to distant parts of the body before it is found.

Less common types of lung cancer include typical and atypical carcinoid tumors, such as large cell undifferentiated carcinoma. These tumors usually start in the neuroendocrine cells that line organs such as the lung and small intestine. Neuroendocrine cells are special cells that are like both nerve cells and endocrine (hormone-producing) cells. Mesothelioma is another type of cancer that can originate in the lungs as well as the abdomen, heart and chest. It is associated with exposure to asbestos and can take 20 to 50 years to develop after exposure.

Being diagnosed with lung cancer is overwhelming, and you will hear a great deal of new information. To fully understand your diagnosis and to be aware of the treatments available to you, including clinical trials, you should know the specific type of lung cancer you have. If you’re not sure, ask your medical team.

Table 1. Classification of lung cancer

Type Frequency (among all lung cancers) Where it's usually found Other features
Non-small cell cancer (NSCLC) 80-85% (See subtypes) The exact type of NSCLC must now be distinguished for optimal therapy.
  ▪ Adenocarcinoma 35-50% Glands of the lungs that produce mucus; often in the outer edges of the lung This is the most common type of lung cancer overall, in women, and in people who have never smoked. Type most often associated with identified genetic abnormalities.
  ▪ Squamous cell
20-25% Lining of the bronchial tubes; usually in the center parts of the lung This type is highly associated with tobacco smoking.
  ▪ Large cell
10-15% Can occur anywhere in the lung but usually near the surface at the outer edges of the lung This type grows more quickly than the other two subtypes.
Small cell cancer (SCLC) 15-20% In the center of the lung, with invasion of the hilar and mediastinal areas and with disease in nearby lymph nodes The cancer cells multiply rapidly and form large tumors that can spread throughout the body; current and former smoking is almost always the cause.


Know Your Medical Team

Depending on your diagnosis and type of treatment, your medical team will be made up of several individuals with different specialties:

Diagnostic radiologist – diagnoses diseases by using imaging tests such as computed tomography, magnetic resonance imaging, ultrasound, and X-rays. Some diagnostic radiologists specialize in radiation oncology. An interventional radiologist may use imaging tests as guides while performing biopsies.

Medical oncologist – treats cancer using medicines such as chemotherapy, targeted therapy and immunotherapy.

Oncologist – specializes in treating cancer. As the primary doctor for your cancer, your oncologist may refer you to other specialists for additional treatment.

Palliative care specialist – or pain management specialist focuses on managing the side effects and pain from cancer.

Pathologist – examines the tissue sample taken during a biopsy to diagnose the type of cancer and stage it. The pathologist also prepares and sends tissues for molecular testing and immune testing when appropriate.

Patient navigator – helps people with the logistics regarding a cancer diagnosis and treatment, including appointment locations, insurance and payment systems, support and advocacy groups and more.

Pulmonologist – diagnoses and treats lung diseases and breathing problems, some of which may be caused by cancer or its treatment.

Radiation oncologist – specializes in treating cancer with radiation therapy.

Respiratory therapist – evaluates and treats people who have breathing problems or other lung disorders.

Thoracic surgeon – treats diseases of the lungs and chest with surgery. Your thoracic surgeon also may be trained in surgical oncology.

Five Things You Should Know About Lung Cancer

As with many other types of cancer, lung cancer is not just one disease. Instead, there are different types of lung cancer, classified according to the specific tissue in the lung in which they develop. Determining the classification of lung cancer and the stage of disease is important because treatment is selected according to the type and stage. Learn about the diagnosis and staging of lung cancer.

Although the overwhelming cause of lung cancer is smoking, not all people with lung cancer are smokers. In fact, the most common type of non-small cell lung cancer (adenocarcinoma) occurs most often in people who have never smoked. You may not have to smoke to get lung cancer, but if you do smoke, you have to quit! Quitting is not easy and it may take several attempts before you’re successful, but you can get help from several resources. Ask your doctor for help.

As researchers discover more information about how lung cancer develops, they are finding genetic abnormalities that can be targets for newer types of drugs. These genetic abnormalities are leading the way for personalized treatment of lung cancer, with treatment selected according to the specific characteristics of an individual tumor. Personalized treatment is also referred to as precision treatment.

Treatments for lung cancer may cause side effects, but many ways to manage side effects now exist. Talk to your doctors about the potential side effects of your treatment options and ask about ways to prevent these side effects. During treatment, tell your doctor or other member of your health care team about symptoms you have so that they can be managed before they become severe.

A diagnosis of lung cancer is overwhelming, and it’s easy to feel as if your life is out of control. But you have the power to overcome many challenges of lung cancer. Don’t be afraid to ask your doctor about treatment options and to state your preferences. Take good care of yourself by getting proper nutrition, exercise and sleep. Do whatever it takes to help you heal and feel physically and emotionally healthy, whether it’s meditation, yoga, relaxation techniques, spirituality or counseling. Spend time with family and friends and be specific about what you need – and don’t need – from them. Enjoy your favorite activities. Live every day to its fullest.


Things to Remember

  1. Diagnostic and treatment approaches are always advancing. Molecular biomarkers identify gene mutations that drive the growth of some lung cancers. If your tumor tests positive for a biomarker, your medical team may recommend an approved molecular therapy or participation in a clinical trial. Ask your medical team if biomarker testing is right for you.
  2. Your medical team is comprehensive. You will work with a variety of professionals, such as an oncologist, pulmonologist, thoracic surgeon, respiratory therapist, pain management specialist and more, to guide you through the physical and emotional stages of your treatment. (See "Know Your Medical Team" above.)
  3. Much cancer-related pain can be managed. The biggest myth about cancer-related pain is that it is something people with cancer must endure. There are now many ways to relieve cancer-related pain, and it’s important to understand these options and find out which option will work best for you. Ask your medical team to connect you with a pain management specialist.
  4. Quit smoking now — it CAN help. If you think it’s too late to quit smoking after getting a lung cancer diagnosis, think again. Continuing to smoke not only increases your chance of a second cancer developing but it also can heighten the side effects from radiation therapy, lessen the effectiveness of chemotherapy and make it harder to recuperate after surgery. Quitting is challenging, especially during treatment, so don’t go it alone.
  5. You are your own best advocate. You can play a significant role in your own care by being educated and motivated. Ask your medical team about treatment options and clinical trials. Seek a second opinion. Speak up about side effects and pain. Take good care of yourself by getting proper nutrition, exercise and sleep. Do whatever it takes to help you heal and feel physically and emotionally healthy, whether it’s meditation, yoga, relaxation techniques, spirituality or counseling.

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