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What is lung cancer?

All of the normal cells in your body have very specific jobs and functions. For example, intestine cells absorb vitamins, minerals and other nutrients from food; red blood cells carry oxygen throughout the body; and white blood cells fight infections. Normal cells stop growing and dividing when they get old. Normal cells also die if they are injured. 

Cancer cells do not function normally; they continue to divide and multiply, and do not die when they are supposed to. 

Every cell contains genes, which are the “brains” that tell the cell what to do. When a cell’s genes are mutated (damaged or changed) cancer may develop. Some of these changes are inherited (passed down from parent to child), but others may occur as a result of exposure to certain toxins, such as cigarette smoke, radon and asbestos. When these mutations in genes cause cells to multiply uncontrollably, a mass of cancer tissue, called a tumor, can develop. 

Cancer cells can also spread through the blood stream to other organs or invade nearby lymph nodes (small collections of white blood cells scattered throughout the body) and spread through the lymph system. When cancer cells spread through any of these methods, they metastasize (travel to other organs and form new tumors). 

Common lung cancer metastasis sites include the brain, bones, adrenal glands (endocrine glands that release hormones), and liver. 

Only cancers that begin in the lungs are called “lung cancer.” Cancer from other parts of the body may spread (or metastasize) to the lungs, but these cancers are not called lung cancer. For example, breast cancer that spreads to the lungs is still breast cancer and will be treated as breast cancer, not lung cancer. Lung cancer that spreads to the liver is treated as lung cancer, not liver cancer.

Types of lung cancer

The two main types of lung cancer are: small-cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). The most common sub-types of NSCLC based on histology are:

  • Adenocarcinoma 
  • Squamous cell carcinoma 
  • Large cell carcinoma 

The histology of your lung cancer can be determined by a pathologist who looks at a sample of your tumor with a microscope. 

There are also other, less common sub-types of NSCLC.

If you have NSCLC, it is important to know your subtype so that your medical team can develop the right treatment plan for you. The majority of lung cancers are NSCLC, and most cases of NSCLC are adenocarcinoma. SCLC tends to grow and spread more rapidly and cause symptoms sooner than NSCLC. For these reasons, treatments for SCLC may differ from those for NSCLC.

What is staging and why is it important?

After your lung cancer is diagnosed, your doctors will determine the type of lung cancer you have and the stage of the disease. Staging is based on the tumor’s size, location, and evidence of spread to lymph nodes and other organs. Staging is needed to help determine your treatment plan. 

Non-Small Cell Lung Cancer (NSCLC) 

Stage I NSCLC

Stage I 

A tumor up to 5 cm wide that has not spread to any lymph nodes or other organs is classified as stage I. These tumors are usually resectable (able to be removed surgically). High-dose radiation therapy may also be used for these tumors (see page 23 for more information). 

  • Stage IA 
    • tumor 3 cm or smaller 
  • Stage IB 
    • tumor 3-5 cm wide in any direction 
Stage II NSCLC

Stage II 

Stage II cancers may be a little larger than stage I, and/or may have spread to lymph nodes on the same side of the chest (hilar lymph nodes), and/or may have begun to invade other structures within the chest. These tumors are usually resectable. 

  • Stage IIA 
    • tumor 5-7 cm wide in any direction with no spread of cancer to lymph nodes OR 
    • less than 5 cm, but spread to lymph nodes on the same side of the chest 
  • Stage IIB 
    • tumor 7 cm or wider in any direction with no spread of cancer to lymph nodes OR 
    • 5-7 cm wide, but spread to lymph nodes on the same side of the chest OR 
    • tumor beginning to invade structures within the chest OR 
    • more than one tumor in the same lobe of the lung 
Stage III NSCLC

Stage III 

A tumor that has spread to the center of the chest (mediastinum) on the same side as the tumor OR has spread to lymph nodes beyond the same side of the chest, but does not appear to have spread to other organs outside the chest is classified as stage III. Often, stage III tumors are unresectable (unable to be removed surgically). Patients with stage III disease are assessed individually for resection, which may be performed after chemotherapy and/or radiation. 

  • Stage IIIA 
    • spread to lymph nodes in the center of the chest (mediastinal lymph nodes
  • Stage IIIB 
    • spread to lymph nodes on the opposite side of the chest or in the lymph nodes above the collarbone OR 
    • involves major structures, such as the heart or arteries 
  • Stage IIIC 
    • same as Stage IIIB, but more than one tumor is found AND/OR 
    • the tumor has spread to other areas in the chest cavity 
Stage IV NSCLC

Stage IV 

Cancer accompanied by pleural effusion (a fluid build-up between the lungs and the chest wall that has cancer cells) or that has metastasized (spread) to other parts of the body is classified as stage IV. Although stage IV cancers are generally not curable, treatments may help you live longer and with an improved quality of life. 

Small-cell Lung Cancer (SCLC) 

Limited-stage SCLC

Limited-stage SCLC is cancer present in only one lung, which may have spread to surrounding lymph nodes. Treatment for limited-stage SCLC generally involves both chemotherapy and radiation therapy. 

Extensive-stage SCLC

Extensive-stage SCLC is cancer that has spread to both lungs, lymph nodes far from the original cancer, or other parts of the body. As with other advanced cancers, extensive-stage SCLC is generally not curable, but there are treatments available that may help you live better and longer. 

How will my doctors find out the stage of my cancer?

Your doctors will determine the stage of your cancer by using any combination of several procedures:

  • Computed tomography (CT) scans are sophisticated x-rays that show the body in cross-sections. These cross-sections are very good at showing the location and size of tumors and enlarged lymph nodes. They may also identify bone lesions or other sites of disease.
  • Positron emission tomography (PET) scans can help determine where tumors are in the body. Because cancer cells grow faster than normal cells, they consume more sugar. A small amount of special dye that contains sugar is injected into a vein, and a PET machine is used to see where the sugar builds up which identifies the location of cancer sites.
  • Bronchoscopy is a procedure in which a doctor puts a small, flexible camera into the airway to look for tumors. The bronchoscope may have tools to remove a small sample (biopsy) of the tumor or lymph nodes for testing.
  • Endobronchial ultrasound (EBUS) is a specialized type of bronchoscopy that uses sound waves to create an image of the tumor and nearby tissues to help the doctor find tumors or decide what area to biopsy.
  • Navigational bronchoscopy uses CAT scans and computer software to guide the physician to the target tissue. This form of bronchoscopy may be used when a tumor exists in the smallest parts of the airways, or to help doctors better find the right spot to take a standard biopsy.
  • Bone scans create pictures of the bones. A special dye is injected into a vein, and a camera is used to see the dye. This tells doctors how healthy the bones are and whether they have any tumors in them. If you’ve recently had a PET scan, you likely will not need a bone scan.
  • Magnetic resonance imaging (MRI) uses magnetic fields to produce detailed images of the body. MRI is particularly useful for finding abnormal growths in the brain.