What is Lung Cancer?

Lung cancer is tumor growth in the lung tissue. It is the most common cause of cancer deaths in the US and the second most diagnosed cancer in the US after breast cancer. The main cause of lung cancer is cigarette smoking but other major risk factors include exposure to secondhand smoke, exposure to harmful chemicals and pollution in the environment, being over 65, genetics, and family history.

Harmful Chemicals in Tobacco

Each puff of tobacco smoke contains thousands of compounds, of which at least 60 are known carcinogens. Therefore, it is not surprising that according to the 2004 Surgeon General’s report (The Health Consequences of Smoking: A Report of the Surgeon General) there is a clear relationship between tobacco smoking and cancers of the lungs, larynx, oral cavity, pharynx, esophagus, pancreas, bladder, kidney, cervix, stomach, colon, rectum, and liver. The most important carcinogens in tobacco are polycyclic aromatic hydrocarbons (PAHs), N-nitrosamines, aromatic amines, 1,3-butadiene, benzene, aldehydes, and ethylene oxide because of their carcinogenic potency and levels in cigarette smoke. Carcinogens cause cancer via various mechanisms including:

  1. Changing the structure of the DNA
  2. Causing errors in the DNA during replication
  3. Silencing of tumor suppress genes
  4. Activation of oncogenes

Classes of Lung Cancer

Lung cancer falls into two main classes, i.e. small cell and non-small cell lung cancer of which non-small cell is more common and small cell more aggressive. Small cell lung cancer appears small and round under a microscope while the cells of non-small cell lung cancer appear large.

Signs, Symptoms, and Treatment of Lung Cancer

Signs and symptoms of lung cancer depend on whether the tumor is in the primary location or has metastasized. Primary symptoms include coughing, hoarseness, difficulty swallowing, difficulty breathing, spitting blood (hemoptysis), recurrent respiratory infection, and chest pain. Symptoms of metastatic lung cancer depend on which organ is affected. For example, lung cancer spread to the bone can cause deep pain, especially in the backbone, thighbones, and ribs. Lung cancer spread to the brain can cause vision problems, seizures, weakness on one side of the body, and headaches.

Diagnosis of Lung Cancer

Lung cancer is diagnosed by medical history, physical examination, imaging test, sputum cytology (using a microscope to look at cells in the sputum), and biopsy. Early signs can come from the evaluation of carcinogen biomarkers in the urine, blood, and breath.

Figure 1. Respiratory system. Wiki Commons.

Avoiding Lung Cancer

The best way to avoid lung cancer is to quit smoking or not to smoke if you don’t already have the habit. Another thing you can do is to avoid exposure to secondhand smoke and harmful chemicals. You can avoid exposure to chemicals at work by taking necessary safety precautions to minimize inhalation e.g., wearing a respirator. Two examples of carcinogenic chemicals to avoid are asbestos and radon. Radon is a colorless and odorless radioactive element that you may be exposed to at home right now without knowing it. Therefore, make sure that your home is tested and that you take the necessary steps to mitigate against it. Asbestos is a naturally occurring mineral that was used in construction many years ago due to its ability to resist heat and provide good insulation. However, it was later discovered to cause cancer when its tiny dust particles are inhaled. Therefore, it is now banned for use in construction.   


Centers for Disease Control and Prevention (US); National Center for Chronic Disease Prevention and Health Promotion (US); Office on Smoking and Health (US). How Tobacco Smoke Causes Disease: The Biology and Behavioral Basis for Smoking-Attributable Disease: A Report of the Surgeon General. Atlanta (GA): Centers for Disease Control and Prevention (US); 2010. 5, Cancer. Available from: https://www.ncbi.nlm.nih.gov/books/NBK53010/

Zelman, M. (2015). Human Disease – A Systematic Approach (8th Edition). Publisher: Pearson Inc. – Chapter: 4 (Neoplasms)

Courtney Simons
Courtney Simons is a food science professor. He holds a BS degree in food science and a Ph.D. in cereal science from North Dakota State University.
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