Lung cancer is the uncontrolled growth of abnormal cells in one or both lungs. These abnormal cells do not carry out the functions of normal lung cells and do not develop into healthy lung tissue. As they grow, the abnormal cells can form tumors and interfere with the functioning of the lung, which provides oxygen to the body via the blood.
The Genetic Basis of Lung Cancer
All cells in the body contain the genetic material called deoxyribonucleic acid (DNA). Every time a mature cell divides into two new cells, its DNA is exactly duplicated. The cells are copies of the original cell, identical in every way. In this way our bodies continually replenish themselves. Old cells die off and the next generation replaces them.
A cancer begins with an error, or mutation, in a cell’s DNA. DNA mutations can be caused by the normal aging process or through environmental factors, such as cigarette smoke, breathing in asbestos fibers, and to exposure to radon gas.
Researchers have found that it takes a series of mutations to create a lung cancer cell. Before becoming fully cancerous, cells can be precancerous, in that they have some mutations but still function normally as lung cells. When a cell with a genetic mutation divides, it passes along its abnormal genes to the two new cells, which then divide into four cells with errors in their DNA and so on. With each new mutation, the lung tissue cell becomes more mutated and may not be as effective in carrying out its function as a lung cell. At a later stage of disease, some cells may travel away from the original tumor and start growing in other parts of the body. This process is call metastasis and the new distant sites are referred to as metastases.
Primary Versus Secondary Lung Cancer
Primary lung cancer starts in the lungs. The cancer cells are abnormal lung cells. Sometimes, people will have cancer travel from another part of their body or metastasize to their lungs. This is called secondary lung cancer because the lungs are a secondary site compared to the original primary location of the cancer. So, for example, breast cancer cells which have traveled to the lung are not lung cancer but rather metastatic breast cancer, and will require treatment prescribed for breast cancer rather than lung cancer.
Symptoms of Lung Cancer
It’s important to report any unusual physical feelings to your doctor. Often, these unusual feelings can be attributed to other causes, such as bronchitis. But a doctor should check anything that is unusual or worrisome. The signs and symptoms of lung cancer can take years to develop and they may not appear until the disease is advanced.
Symptoms of lung cancer that are in the chest:
- Coughing, especially if it persists or becomes intense
- Pain in the chest, shoulder, or back unrelated to pain from coughing
- A change in color or volume of sputum
- Shortness of breath
- Changes in the voice or being hoarse
- Harsh sounds with each breath (stridor)
- Recurrent lung problems, such as bronchitis or pneumonia
- Coughing up phlegm or mucus, especially if it is tinged with blood
- Coughing up blood
If the original lung cancer has spread, a person may feel symptoms in other places in the body. Common places for lung cancer to spread include other parts of the lungs, lymph nodes, bones, brain, liver, and adrenal glands.
Symptoms of lung cancer that may occur elsewhere in the body:
- Loss of appetite or unexplained weight loss
- Muscle wasting (also known as cachexia)
- Headaches, bone or joint pain
- Bone fractures not related to accidental injury
- Neurological symptoms, such as unsteady gait or memory loss
- Neck or facial swelling
- General weakness
- Blood clots
Diagnosing Lung Cancer
If lung cancer is suspected as a result of a screening procedure, a small piece of tissue from the lung must be examined under a microscope to look for cancer cells. Called a biopsy, this procedure can be performed in different ways. In some cases, the doctor passes a needle through the skin into the lungs to remove a small piece of tissue; this procedure is often called a needle biopsy.
In other cases, a biopsy may be done during a bronchoscopy. To perform a bronchoscopy, the doctor inserts a small tube through the mouth or nose and into the lungs. The tube, which has a light on the end, allows the doctor to see inside the lungs and to remove a small tissue sample.
When a person is diagnosed with lung cancer, looking at biopsied cells under the microscope also helps doctors determine the type of lung cancer. It is important to know the specific type because this information helps doctors recommend the best treatment.