Lung cancer is the uncontrolled growth of abnormal cells that start off in one or both lungs; usually in the cells that line the air passages. The abnormal cells do not develop into healthy lung tissue, they divide rapidly and form tumors. As tumors become larger and more numerous, they undermine the lung’s ability to provide the bloodstream with oxygen.
What causes cancer?
Smoking causes the majority of lung cancers — both in smokers and in people exposed to secondhand smoke. But lung cancer also occurs in people who never smoked and in those who never had prolonged exposure to secondhand smoke. In these cases, there may be no clear cause of lung cancer.
Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death. Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide. This leads to a mass of abnormal cells that grows out of control.
Lung cancer occurs when a lung cell’s gene mutation makes the cell unable to correct DNA damage and unable to commit suicide. Mutations can occur for a variety of reasons. Most lung cancers are the result of inhaling carcinogenic substances.
Carcinogens are a class of substances that are directly responsible for damaging DNA, promoting or aiding cancer. Tobacco, asbestos, arsenic, radiation such as gamma and x-rays, the sun, and compounds in car exhaust fumes are all examples of carcinogens. When our bodies are exposed to carcinogens, free radicals are formed that try to steal electrons from other molecules in the body. These free radicals damage cells and affect their ability to function and divide normally.
About 87% of lung cancers are related to smoking and inhaling the carcinogens in tobacco smoke. Even exposure to second-hand smoke can damage cells so that cancer forms.
Cancer can be the result of a genetic predisposition that is inherited from family members. It is possible to be born with certain genetic mutations or a fault in a gene that makes one statistically more likely to develop cancer later in life. Genetic predispositions are thought to either directly cause lung cancer or greatly increase one’s chances of developing lung cancer from exposure to certain environmental factors.
What are the symptoms of lung cancer?
Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and how big the tumor is. Lung cancer symptoms may take years before appearing, usually after the disease is in an advanced stage.
Many symptoms of lung cancer affect the chest and air passages. These include:
- Persistent or intense coughing
- Pain in the chest shoulder, or back from coughing
- Changes in color of the mucus that is coughed up from the lower airways (sputum)
- Difficulty breathing and swallowing
- Hoarseness of the voice
- Harsh sounds while breathing (stridor)
- Chronic bronchitis or pneumonia
- Coughing up blood, or blood in the sputum
If the lung cancer spreads, or metastasizes, additional symptoms can present themselves in the newly affected area. Swollen or enlarged lymph nodes are common and likely to be present early. If cancer spreads to the brain, patients may experience vertigo, headaches, or seizures. In addition, the liver may become enlarged and cause jaundice and bones can become painful, brittle, and broken. It is also possible for the cancer to infect the adrenal glands resulting in hormone level changes.
As lung cancer cells spread and use more of the body’s energy, it is possible to present symptoms that may also be associated with many other ailments. These include:
- Unexplained weight loss
- Pain in joints or bones
- Problems with brain function and memory
- Swelling in the neck or face
- General weakness
- Bleeding and blood clots