Only cancers that begin in the lungs are called “lung cancer.” Sometimes cancer from other parts of the body may spread to the lungs, but it is 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.

Cancer forms when cells multiply out of control. 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 our 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 are different. They do not function normally, they keep dividing and multiplying, and they do not die when they grow old. They can also spread through the blood stream, or invade nearby lymph nodes and spread through the lymph system. When cancer cells spread through any of these methods, they can metastasize. Common lung cancer metastasis sites include the brain, bones and liver.

Why does cancer happen?
Types of lung cancer
What is staging, and why is it important?
How will doctors find out the stage of my cancer?

Why does cancer happen?

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

Types of lung cancer

The two main types of lung cancer are: small-cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC is further subtyped as:
    •  Adenocarcinoma
    •  Squamous cell carcinoma
    •  Large cell carcinoma

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 (about eight out of 10) are NSCLC, and most cases of NSCLC (about five out of 10) are adenocarcinoma.

Small-cell lung cancers tend 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 and whether it has spread to any lymph nodes in the area or to other organs.

Non-small cell lung cancer (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.

Stage IA:
    •  3 cm or smaller
Stage IB:
    •  3-5 cm wide in any direction

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

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

Stage III
A tumor that 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.

Stage IIIA:
    •  spread to lymph nodes in the center of the chest
Stage IIIB:
    •  spread to lymph nodes on the opposite side of the chest OR
    •  involves major structures, such as the heart or arteries

Stage IV
Cancer accompanied by pleural effusion or that has metastasized to other parts of the body is classified as stage IV. Although stage IV cancers are difficult to cure, there are treatments available that may help you live longer and better.

Small-cell lung cancer (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 is cancer that has spread to both lungs, lymph nodes far from the original cancer, or to other parts of the body. As with other advanced cancers, extensive-stage SCLC can be difficult to cure, 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.   

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. When a small amount of special dye that contains sugar is injected into a vein, a PET machine is used to see where the sugar builds up.

Bronchoscopy is a procedure in which a doctor puts a camera down the airway to look for tumors and possibly perform a biopsy using a needle.   

Endobronchial ultrasound (EBUS) is a newer, more specialized type of bronchoscopy that uses sound waves to create an image of the tumor and nearby tissues to help the doctor decide what area to biopsy.

Navigational bronchoscopy uses CT scans, computer software, and special very small devices to guide the bronchoscopy procedure. 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.

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.

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This information is not designed to be a substitute for medical advice provided by your treatment team.