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Lung Cancer

  • Definition

    Article updated and reviewed by Kevin Knopf, MD, MPH; Director of Clinical Research, Annapolis Oncology Center and Associate Staff, Johns Hopkins Oncology Center on July 22, 2005.

    cancer is a disease characterized by the uncontrolled growth of abnormal cells. lung cancer is any type of malignant (cancerous) growth in the lungs. Lung cancer is the most common cause of cancer death in both men and women. There will be 158,000 estimated deaths from lung cancer in 1999, which represents 28 percent of all cancer deaths. (Source: The American Cancer Society)


    The lung is the main organ of the respiratory system. Its main function is respiration (the exchange of gases between the environment and the body). Air enters the nose where it is filtered, warmed and humidified. After passing through the trachea (windpipe), the air travels into the lungs and through the tracheobronchial system, which consists of the bronchi (a system of branching airway tubes that become smaller as they reach deeper into the lung), the bronchioles (the smallest of the bronchi) and the alveoli (balloon-like sacs located at the end of the bronchi).

    Within the lungs and the tracheobronchial system is a lining called the epithelium, and within the epithelium are cells. The function of the cells is to divide, reproduce and repair worn-out or injured lung tissue and to allow for growth. If the cells lose their ability to control division, excess growth takes place, tumors form, and lung cancer emerges.

    There are four main types of lung cancer - adenocarcinoma, squamous cell carcinoma, small cell carcinoma and large cell carcinoma. Small cell lung cancer is grouped by itself and the other three types – adenocarcinoma, squamous cell carcinoma, and large cell carcinoma are collectively referred to as Non-small cell carcinoma of the lung. The type of lung cancer is determined by the appearance of the cancerous cells under a microscope.

    • Small cell lung cancer (SCLC) is sometimes called oat cell cancer, because the cancer cells look like oats when they are viewed under a microscope. It develops most often in the bronchial submucosa (a layer of tissue beneath the epithelium - the lining of the lungs) and is found predominately in people who are heavy smokers. This type of cancer spreads rapidly and is more likely than other types to have metastasized (cancer cells from the original tumor have spread to another part of the body). This type of lung cancer makes up about 20 to 25 percent of all cases. Virtually all patients with small cell lung cancer have a smoking history.
    • Squamous cell carcinoma, makes up 25 to 30 percent of all lung cancer cases. When viewed under a microscope, the squamous cells look like fish scales. This type of lung cancer often begins in the bronchi and may remain in the chest without spreading for longer periods than other cancers.
    • Adenocarcinoma accounts for about 25 to 30 percent of all lung cancers. When viewed under a microscope, the cancerous cells are cube or column shaped, and they grow in patterns that are usually seen in the glands. It often grows along the outer edges of the lungs and under the tissue lining the bronchi. This is the most common type of lung cancer. Non-smokers who get lung cancer almost always get adenocarcinoma. There is a subtype of adenocarcinoma called Bronchoalveolar carcinoma.
    • Large cell carcinomas make up about 10 to 20 percent of all lung cancer cases. Cells that are not diagnosed as squamous, adenocarcinoma or SCLC, are categorized under this heading. These cancers are found most often in the smaller bronchi.

    The number one cause of lung cancer is cigarette smoking, representing 85 to 90 percent of all cases. Cigar and pipe smoking are also associated with lung cancer. Other causes include exposure to radon, asbestos, nickel, chloromethyl ether, chromium, beryllium and arsenic (a byproduct of copper), as well as exposure to passive smoke or "secondhand" smoke.

    A person is "at risk" of developing lung cancer if they:

    • smoke
    • are over the age of 50
    • work in industries where substances such as asbestos, nickel, chloromethyl ether, chromium, beryllium and arsenic are used
    • have or have had a lung disease
    • have a family history of lung cancer
    • are former smokers
    • have been exposed to secondhand smoke over many years
    • have been exposed to radon

    Lung cancer often does not produce symptoms in the early stages. When symptoms do occur, they are a result of tumor growth, pressure and invasion on nearby structures and nerves, regional growths or metastasis.

    If the cancer originated and grew in the bronchi and spread to nearby lymph nodes, the symptoms may include:

    • coughing (when a tumor grew and blocked a passage)
    • coughing up blood
    • chest pain
    • shortness of breath
    • pneumonia
    • hoarseness (caused by pressure on a nerve)
    • difficulty in swallowing (caused by an obstruction of the esophagus)
    • swelling of the neck, face and upper extremities (caused by pressure on blood vessels)
    • fatigue
    • loss of appetite
    • loss of weight

    If the cancer originated and grew at the top of the lung, the symptoms may include:

    • Pancoast's syndrome (weakness and pain in the shoulder, arm and hand, caused by pressure on the nerves)

    If the cancer has metastasized and traveled to other parts of the body, the symptoms may include:

    • Metastasis to brain: headache, weakness, behavioral changes, speech problems and memory lapses.
    • Metastasis to other parts: pain, bone fractures, jaundice and blood clots.

    Additionally, lung tumors also may alter the production of hormones (called Paraneoplastic syndrome) that regulate body functions, causing:


    If lung cancer is suspected, the person will have their medical history taken, a physical examination, and a variety of tests to confirm the diagnosis.

    During the physical exam, the doctor will look for lymph node enlargement in the neck or in the region above the collarbones, liver enlargement, abnormal abdominal enlargement, and signs of a lung mass. Simple hand palpitations (lightly pressing of areas) are used to find enlargements, while a stethoscope is used to detect lung mass. The doctor will listen for decreased breath sounds, unusual lung noises and areas of dullness in the lung.

    The tests may include the following:

    • chest x-ray to look for growths
    • a sputum test (phlegm coughed up from the lung) to detect cancerous cells
    • biopsy (the surgical removal of a small piece of tissue for microscopic examination). There are various methods to obtain a biopsy. One way is with a procedure called a bronchoscopy. A bronchoscopy involves inserting a flexible lighted tube (a bronchoscope) into the person's mouth or nose and guiding it into the bronchi. Other instruments can then be passed through the bronchoscope to remove the sample. Another method is called a percutaneous needle biopsy, in which a needle is inserted through the skin into the lung. With the help of ultrasound or a ct scan, the doctor is able to guide the needle to the cancerous growth and remove a sample.
    • pulmonary function test, called a spirometry. Using a machine called a spirometer, the doctor is able to record the rate at which a person exhales air from the lungs and the total volume exhaled, thus indicating a narrowing or obstruction in the airways.


    Once the diagnosis of lung cancer is made, further staging studies are done to determine the spread of the disease and the appropriate treatment method. These studies include computed tomography (CT or cat scan), a bone scan and a PET scan.

    The CT/CAT scan is a series of x-rays taken as a scanner revolves around the body. A computer then receives the x-ray images and creates a cross-sectional picture of the area being examined.

    A bone scan, also called a radionuclide or nuclear medicine scan, involves injecting a radioactive substance into the body. An instrument then scans the body to measure radiation levels. A PET scan is similar to a bone scan except it gives information on all the organs of the body. It is especially useful to determine if the lung cancer has spread outside of the lung. It is important to realize, though, it is not 100% accurate; for example areas of cancer that range 0.6 centimeters to one centimeter will often not be visible on PET scan.

    Once the additional tests are done, the doctor will determine what stage the cancer is in and base treatment decisions on this information.


    Standard treatment for patients with lung cancer is of limited effectiveness in all but the most localized tumors. For this reason, patients are encouraged to consider participating in clinical trials (research studies) designed to evaluate new approaches to therapy.

    Surgery, radiation therapy and chemotherapy (used alone or in various combinations) are the standard methods used to treat lung cancer. The choice of treatment depends on many factors, including the type of tumor, the extent of the disease when it is diagnosed, the age and general health of the patient and other variables. The first question to ask is whether the lung cancer is caught at an early enough stage to allow for surgery with curative intent.

    Surgical procedures that may be employed include wedge or segmental resection (removal of a portion of the affected lungs), lobetomy (removal of the entire lobe of the lung) or pneumonectomy (removal of the entire right or left lung).

    radiation therapy is usually given by external beam, using machines located outside the body that deliver x-rays or electrons to the location of the tumor. The radiation dose is based on the size and location of the tumor.

    Some patients first receive external therapy to a wide area that includes the primary tumor and surrounding tissue. After the initial treatments, a smaller area is treated and a final treatment area that may be quite small. Radiation here is referred to as a "boost." Like surgery, radiation therapy is called local treatment, because it affects only the cells in the area being treated.

    chemotherapy (treatment with anticancer drugs) is a systemic treatment - the drugs enter the bloodstream and travel through the body, affecting cancer cells outside the lung area. Drugs given to treat lung cancer may be given by mouth or injection to a muscle or vein.. Most chemotherapy is taken on an outpatient basis. A newer type of chemotherapy called targeted therapy is exemplified by Tarceva, a pill with less side effects than traditional chemotherapy used in refractory cases of lung cancer.


    What type of cancer is it?

    Are there tests to identify if the cancer has spread?

    Is surgery indicated?

    Will chemotherapy or radiation therapy be used in your treatment regime?

    What are the benefits and risks of the treatment options?

    Is there a clinical trial I can participate in?

    What is the short and long term prognosis?


    Editorial review provided by VeriMed Healthcare Network.