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Understanding Lung Cancer

Unless you have previous experience with the disease, it is likely that you knew little about lung cancer when the one you are caring for was first diagnosed. It is also quite possible that what you have heard about the disease is inaccurate or misinformed. As a caregiver for someone who has lung cancer, you may find it helpful to have a basic understanding of the disease. The following pages provide a simple overview of lung cancer. Then, if you want to learn more about lung cancer, there are many excellent resources available, including Lung Cancer Choices, 6thEdition.

Another excellent resource is the National Cancer Institute’s (NCI) website,; much of the following is adapted from the free resources provided by NCI.

Your Lungs

We will begin at the most basic level. Your lungs are a pair of large organs in your chest that help your body get the oxygen that it requires. Air enters your body through your nose or mouth before it passes through your windpipe (trachea), through each bronchus, and into your lungs.

When you breathe in, your lungs expand with air; this is how your body gets oxygen. When you breathe out, air goes out of your lungs; this is how your body gets rid of carbon dioxide.

The right lung has three parts, called lobes. The left lung is smaller and has two lobes. Inside the chest are two thin layers of tissue called the pleura. One layer of pleura covers the lungs and the other layer lines the inside of your chest; it is as if your lungs are inside two balloons.

Cancer Cells

Cancer begins in cells, the building blocks that make up all tissues and organs of the body, including the lungs. Healthy cells in the lungs and other parts of the body grow and divide to form new cells as they are needed. When healthy cells grow old or get damaged, they die, and new cells take their place. Sometimes, this process goes wrong. New cells form when the body does not need them, and old or damaged cells fail to die as they should. The buildup of extra cells often forms a mass of tissue, which is referred to as a tumor.

Lung cancer cells can spread by breaking away from a lung tumor. These cells can travel through blood vessels or lymph vessels to reach other parts of the body. This process is called metastasis. After spreading, cancer cells may attach to other tissues and grow to form new tumors that may damage their new host tissues. Not all cancer is the same, and some types are easier to control than others.

When lung cancer spreads from its original place to another part of the body, the new tumor has the same kind of abnormal cells and is referred to by the same name as the original, or primary, tumor. For example, if lung cancer spreads to the bones, the cancer cells in the bones are lung cancer cells. Therefore, this type of cancer, even though it is in the bone, is metastatic lung cancer, not bone cancer. In this situation, cancer that appears in the bone is treated as lung cancer, not bone cancer.

Types of Lung Cancer

Just as there are distinct types of cancer throughout the body, there are also distinct types of lung cancer. As a caregiver, it is essential that you know which type of lung cancer the person with cancer has been diagnosed with; treatment and all aspects of care depend on the type of lung cancer.

Small cell: The cells of small cell lung cancer look small under a microscope. About 1 out of every eight people with lung cancer has small cell lung cancer.

Non-small cell: The cells of non-small cell lung cancer are larger than the cells of small cell lung cancer. Most people, about 7 out of every 8 with lung cancer, have the non-small cell variety. Non-small cell lung cancer does not grow and spread as fast as small cell lung cancer, and the two types of lung cancer call for different treatments. Within non-small cell lung cancer, there are also two distinct classifications: adenocarcinoma and squamous cell cancer.

Staging of Lung Cancer

Staging is the assessment of the extent of spread of the tumor, including spread to lymph nodes and metastasis, when cancer spreads to other parts of the body. The oncologist who is treating the person with cancer will determine how to treat the cancer based on the stage location in the body.

Staging tests that the person with cancer may undergo:

A biopsy: a small piece of tissue is taken from the patient’s affected tissues and examined under a microscope.

CT scan: an x-ray machine linked to a computer takes a series of detailed pictures of the patient’s chest, abdomen, brain, or other parts of the body. First, the patient receives an injection of contrast material in a blood vessel in the arm or hand. In some cases, the patient will also drink a solution containing contrast material. The contrast material makes abnormal areas easier to see on the scan. The pictures from a CT scan can help to determine the lung tumor’s size. The scans can also help to show if cancer has spread to the liver, adrenal glands, brain, or other organs.

PET scan: the health care team of the person with cancer may order a PET scan to get a better view of the tumor in the lung or to find cancer that has spread to other parts of the body. The patient will receive an injection of a small amount of radioactive sugar before the scan. Then, a specialized machine creates computerized pictures of the sugar being used by cells in the body. Because cancer cells use sugar faster than normal cells, areas with cancer cells appear brighter.

MRI: a strong magnet linked to a computer is used to make detailed pictures of the patient’s head or spine. An MRI can show whether cancer has spread to these areas. Sometimes contrast material is used to make abnormal areas show up more clearly on the image.

Bone scan: A small amount of a radioactive substance is injected into a blood vessel. The radioactive substance travels through the patient’s bloodstream and collects in the bones. A machine called a scanner detects and measures the radiation. The scanner uses this data to create images of the patient’s bones. Because higher amounts of the radioactive substance collect in areas where cancer is present, the images can help determine whether cancer has spread to the bones.

Stages for Non-Small Cell Lung Cancer

All non-small cell lung cancers are staged the same way, whether the tumor is determined to be adenocarcinoma or squamous cell lung cancer.

Stage 0

This is called in situ disease, meaning the cancer is “in place” and has not grown into nearby tissues and spread outside the lung.

Stage I

A small tumor that has not spread to any lymph nodes, making it possible for a surgeon to completely remove it. Stage I is divided into 2 substages based on the size of the tumor:

  • Stage IA tumors are 3 centimeters (cm) or less in size.
  • Stage IB tumors are more than 3 cm but 4 cm or less in size.

Stage II

Stage II lung cancer is divided into 2 substages:

  • A stage IIA cancer describes a tumor larger than 4 cm but 5 cm or less in size that has not spread to the nearby lymph nodes.
  • Stage IIB lung cancer describes a tumor that is 5 cm or less in size that has spread to the lymph nodes. A stage IIB cancer can also be a tumor more than 5 cm wide that has not spread to the lymph nodes.

Stage III

Stage III lung cancers are classified as either stage IIIA, IIIB, or IIIC. The stage is based on the size of the tumor and which lymph nodes the cancer has spread to. Stage III cancers have not spread to other distant parts of the body.

Stage IV

Stage IV means the lung cancer has spread to more than 1 area in the other lung, the fluid surrounding the lung or the heart, or distant parts of the body through the bloodstream.

Stages for Small Cell Lung Cancer

Most doctors describe the stages of small cell lung cancer with two stages:

Limited stage: Cancer is found only on one side of the chest.

Extensive stage: Cancer is found in the lung and also in tissues on the other side of the chest.


Lung cancer is in distant organs, such as the brain, or the fluid between the two layers of pleura.

Additional Testing for Non-Small Cell Lung Cancer

Comprehensive Biomarker Testing

Lung cancer is a complex cancer that has known mutations. Biomarkers are molecules in the blood or tissue that can result from mutations in genes. Biomarkers help to link subsets of people diagnosed with non-small cell lung cancer (NSCLC) to certain therapies and can help predict response, resistance, or toxicity to certain drugs.  With improved biomarker testing techniques, an expanding list of molecular targets and more approved and emerging therapies, comprehensive biomarker testing is an essential part of the evaluation and management of all patients diagnosed with NSCLC. See Lung Cancer Choices, 6th Edition, Chapter 2: Comprehensive Biomarker Testing