What is cancer?
The body is made up of hundreds of millions of living cells. Normal body cells grow, divide, and die in an orderly way. During the early years of a person's life, normal cells divide faster to allow the person to grow. After the person becomes an adult, most cells divide only to replace worn-out, damaged, or dying cells.
Cancer begins when cells in a part of the body start to grow out of control. There are many kinds of cancer, but they all start because of this out-of-control growth of abnormal cells.
Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells keep on growing and form new cancer cells. These cancer cells can grow into (invade) other tissues, something that normal cells cannot do. Being able to grow out of control and invade other tissues are what makes a cell a cancer cell.
In most cases the cancer cells form a tumor. But some cancers, like leukemia, rarely form tumors. Instead, these cancer cells are in the blood and bone marrow.
When cancer cells get into the bloodstream or lymph vessels, they can travel to other parts of the body. There they begin to grow and form new tumors that replace normal tissue. This process is called metastasis (muh-tas-tuh-sis).
No matter where a cancer may spread, it is always named for the place where it started. For instance, breast cancer that has spread to the liver is still called breast cancer, not liver cancer. Likewise, prostate cancer that has spread to the bone is called metastatic prostate cancer, not bone cancer.
Different types of cancer can behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That is why people with cancer need treatment that is aimed at their own kind of cancer.
Not all tumors are cancerous. Tumors that aren't cancer are called benign (be-nine). Benign tumors can cause problems – they can grow very large and press on healthy organs and tissues. But they cannot grow into other tissues. Because of this, they also can't spread to other parts of the body (metastasize). These tumors are almost never life threatening.
Lung Cancer Risks Increase From Asbestos and Tobacco Use
Asbestos Lung Cancer Can Spread Quickly to Other Parts of the Body
Studies show an increase in lung cancer among workers exposed to asbestos. This increase is particularly significant among asbestos–exposed workers who smoke. A dose–response relationship exists both for the degree of asbestos exposure and the amount of cigarette smoking.
Asbestos Lung Cancer Explained
Most asbestos lung cancer starts in the lining of the bronchi, the tubes into which the trachea or windpipe divides. However, asbestos lung cancer can also begin in other areas such as the trachea, bronchioles (small branches of the bronchi), or alveoli (lung air sacs). Although lung cancer usually develops slowly, once it occurs, cancer cells can break away and spread to other parts of the body.
The two most common types of lung cancer are small cell lung cancer (SCLC), in which the cancer cells are small and round, and non–small cell lung cancer (NSCLC), in which the cancer cells are larger. Sometimes a cancer has features of both types, and is called mixed small cell/large cell cancer.
Non–small cell lung cancer accounts for almost 80% of lung cancers. Small cell lung cancer accounts for about 20% of all lung cancers. Although the cancer cells are small, they can multiply quickly and form large tumors. The tumors can spread to the lymph nodes and to other organs.
Early–stage asbestos lung cancer may be asymptomatic (without symptoms). The methods used to diagnose asbestos lung cancer include imaging tests, biopsies, and taking phlegm (spit) samples.
Identifying Asbestos Lung Cancer Using CT Scans and Tissue Biopsy
In Early Stages, Asbestos Lung Cancer May Have Few Symptoms
Patients in the early stages of asbestos lung cancer often do not have symptoms. Some early symptoms, present in only about 15% of lung cancer cases, are a persistent cough, chest pain, hoarseness, weight loss, and bloody or rust–colored sputum (spit or phlegm). However, these symptoms could also indicate other diseases.
If your doctor suspects that you have asbestos lung cancer, a full physical examination is warranted. Your doctor may also take a sample of your phlegm (spit). This will be examined under a microscope to see if cancer cells are present.
Asbestos Lung Cancer Biopsy
In many cases, a pathologist will take a tissue sample or biopsy to confirm whether asbestos lung cancer is present.
Types of biopsies include:
· Bronchoscopy: The doctor puts a bronchoscope (a thin, lighted tube) into the mouth or nose and down through the windpipe to look into the breathing passages. Through this tube, the doctor can collect cells or small samples of tissue.
· Needle aspiration: A needle is inserted through the chest into the tumor to remove a sample of tissue.
· Thoracentesis: Using a needle, the doctor removes a sample of the fluid that surrounds the lungs to check for cancer cells.
· Thoracotomy: Surgery to open the chest. This procedure is a major operation performed in a hospital.
· Mediastinoscopy: Using a lighted viewing instrument or scope, the doctor examines the center of the chest (mediastinum) and nearby lymph nodes. Tissue samples are taken from the lymph nodes along the windpipe through a small hole cut into the neck.
Using Imaging Techniques to Detect Asbestos Lung Cancer
Imaging tests that are useful in asbestos lung cancer detection include x–rays, and CT (computed tomography), MRI (magnetic resonance imaging) and PET (positron emission tomography) scans. CT, MRI and PET scans may also help determine how far the cancer has spread (staging).
Radionuclide scanning shows whether cancer has spread to other organs such as the liver. The patient swallows or receives an injection of a radioactive substance. A scanning machine measures the level of radioactivity in certain organs to reveal abnormal areas. A bone scan is a type of radionuclide scanning that indicates whether cancer has spread to the bones. In a bone scan, a radioactive substance is injected into a vein, travels through the bloodstream and collects in areas of abnormal bone growth. The scanner measures the radioactivity levels in these areas and records them on x–ray film.
Note: This document covers only the non-small cell type of lung cancer. The treatment for the 2 main types of lung cancer (small cell and non-small cell) is very different. Much of the information for one type will not apply to the other type. If you are not sure which type of lung cancer you have, it is very important to ask you doctor so you can be sure you get the right information.
Lung cancer is a cancer starts in the lungs. In order to understand lung cancer, it helps to know something about the structure of the lungs and how they work.
The lungs
The lungs are 2 sponge-like organs found in the chest. The right lung has 3 sections, called lobes. The left lung has 2 lobes. The left lung is smaller because the heart takes up more room on that side of the body.
When you breathe in, air enters through your mouth and nose and goes into your lungs through the windpipe (trachea). The trachea divides into tubes called the bronchi, which divide into smaller branches called the bronchioles. At the end of the bronchioles are tiny air sacs known as alveoli. Many tiny blood vessels run through the alveoli. They absorb oxygen from the air you breathe in and pass carbon dioxide from the body into the alveoli to be breathed out when you exhale. Taking in oxygen and getting rid of carbon dioxide are your lungs' main functions.
The lining around the lungs, called the pleura, helps to protect the lungs and allows them to move during breathing.
Below the lungs, a muscle called the diaphragm separates the chest from the belly (abdomen). When you breathe, the diaphragm moves up and down, forcing air in and out of the lungs.
Start and spread of lung cancer
Lung cancer can start in the lining of the bronchi or in other parts of the lung. Lung cancers are thought to start as areas of pre-cancerous changes in the lung. These changes are not a mass or tumor. They can't be seen on an x-ray and they don't cause symptoms.
Over time, these pre-cancerous changes in cells may go on to become true cancer. The cancer makes chemicals that cause new blood vessels to form nearby. These new blood vessels feed the cancer cells and allow a tumor to form. In time, the tumor becomes large enough to show up on an x-ray.
At some point, cancer cells can break away and spread to other parts of the body in a process called metastasis. Lung cancer is often a life-threatening disease because it can spread in this way before it is found.
The lymph system
One of the ways lung cancer can spread is through the lymph system. Lymph vessels are like veins, but they carry lymph instead of blood. Lymph is a clear fluid that contains tissue waste products and cells that fight infection. Lung cancer cells can enter lymph vessels and begin to grow in lymph nodes (small collections of immune cells) around the bronchi and in the area between the lungs. When lung cancer cells have reached the lymph nodes, they are more likely to have spread to other organs of the body. The stage (extent) of the cancer and decisions about treatment are based on whether or not the cancer has spread to the nearby lymph nodes.
Types of lung cancer
There are 2 main types of lung cancer and they are treated differently.
· Small cell lung cancer (SCLC)
· Non-small cell lung cancer (NSCLC)
(If the cancer has features of both types, it is called mixed small cell/large cell cancer. This is not common.)
The information here only covers non-small cell lung cancer. Small cell lung cancer is covered in our document.
Non-small cell lung cancer (NSCLC)
About 9 out of 10 cases of all lung cancers are the non-small cell type. There are 3 main sub-types of NSCLC. The cells in these sub-types differ in size, shape, and chemical make-up.
· Squamous cell carcinoma: About 25% to 30% of all lung cancers are this kind. They are linked to smoking and tend to be found in the middle of the lungs, near a bronchus.
· Adenocarcinoma: This type accounts for about 40% of lung cancers. It is usually found in the outer part of the lung. This type of lung cancer occurs mainly in people who smoke (or have smoked), but it is also the most common type of lung cancer seen in non-smokers. It is more common in women than in men, and it is more likely to occur in younger people than other types of lung cancer.
· Large-cell (undifferentiated) carcinoma: About 10% to 15% of lung cancers are this type. It can start in any part of the lung. It tends to grow and spread quickly, which makes it harder to treat.
Other types of lung cancer
Along with the 2 main types of lung cancer, other tumors can be found in the lungs, too. Some of these are not cancer and others are cancer. Carcinoid tumors, for instance, are slow-growing and usually cured by surgery.
Keep in mind that cancer that starts in other organs (such as the breast, pancreas, kidney, or skin) can sometimes spread (metastasize) to the lungs, but these are not lung cancers. For example, cancer that starts in the kidney and spreads to the lungs is still kidney cancer, not lung cancer. Treatment for these cancers that have spread to the lungs depends on where the cancer started.
How many people get lung cancer?
Most lung cancer statistics include both small cell and non-small cell lung cancers. The American Cancer Society's most recent estimates for lung cancer in the United States are for 2010:
· About 220,520 new cases of lung cancer (both small cell and non-small cell)
· About 157,300 deaths from lung cancer
Lung cancer (both small cell and non-small cell) is the leading cause of cancer death for both men and women. More people die of lung cancer than of colon, breast, and prostate cancers combined. Lung cancer is rare in people under the age of 45.
The average lifetime chance that a man will develop lung cancer is about 1 in 13. For a woman it is 1 in 16. These numbers include both smokers and non-smokers. For smokers the risk is much higher, while for non-smokers the risk is lower.
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