The Basics of Lung Cancer

What is Lung Cancer? 

The leading cause of death for both men and women in the United States, lung cancer is cancer in any portion of the lungs. Lung cancer is nondiscriminatory and can develop in anyone. While smoking does cause most lung cancers, nonsmokers can develop lung cancer. Often, lung cancer is a result of exposure to dangerous chemicals that are inhaled.  

How it Begins 

Like any cancer, lung cancer begins when a cell with damaged DNA begins to duplicate at a rapid rate due to the damage. These cells continue to divide unchecked, and eventually form a tumor. These cells also can metastasize, or travel to other parts of the body and begin growing there, which occurs in high frequency with lung cancer cases. Often, symptoms are not recognized until this has already occurred.  

What exactly is cancer?

No two cases of lung cancer are the same; there are many different types as well as subtypes of lung cancer. The type is dependent on which cells within the lung develop cancer. Pictured below, you can see that the lung has numerous subcomponents, each of which are susceptible to developing cancer.  

Two Main Types  

The two main types of lung cancer are small cell lung cancer, and non-small cell lung cancer.  

  • Small cell lung cancer, or SCLC, can be divided into two types. They comprise about 10-15% of all lung cancer diagnoses. The types of small cell lung cancer are named in honor of the type of cells the cancer is composed of, and how they appear when they are viewed under a microscope. This form of lung cancer is usually associated with cigarette smoking and is usually treated with chemotherapy.  
  • Small cell carcinoma, or oat cell carcinoma, typically begins in the bronchi and spreads rapidly. It is terms “oat cell” because the cells are small and flat under a microscope. This form is linked to inhaling asbestos.  
  • Non-small cell lung cancer, or NSCLC, is more common than SCLC, composing 80-85 percent of lung cancer cases. This form is less likely to metastasize, and typically progresses slower. There are three types of NSCLC: 
  • Adenocarcinoma is often found on the outer area of the lung and develops in the epithelial tissues. This type is commonly seen in both smokers and non-smokers and affects more women than men. This type comprise up to 40% of all lung cancer types and is the most common lung cancer type. 
  • Squamous cell carcinoma is found in the center of the lung, near the bronchus, which is an air tube of the lungs. These account for 25-30% of all lung cancer cases. 
  • Large cell undifferentiated carcinoma can occur in any portion of the lung and is more aggressive than the previous two types of NSCLC. It grows and spreads more rapidly and accounts for 10-15% of all lung cancer diagnoses and is likely to spread to the lymph nodes as well as other parts of the body. 

Rare Lung Cancer Types 

These two types of lung cancer and their relative subtypes are the most common forms of lung cancer. There are other forms of tumors that can develop in the lungs.  

  • Pancoast tumors (superior sulcus tumors) grow in the upper part of the lung and cause problems with the lung structures that surround this area. This type of tumor is rare and is almost always NSCLC. This form of lung cancer is often treated with chemotherapy, radiation, and/or surgery.  
  • Carcinoid tumors in the lungs are also uncommon, and usually grow slower than the other types of lung cancers. This tumor is made of a different type of cancer cells, called neuroendocrine cells. They can be classified further into two groups: typical and atypical. These are extremely rare, slow-growing, and are usually treated with surgery.  

There are a few other types of lung cancer which are much rarer than the previously mentioned.  

  • Adenosquamous carcinoma of the lung is a hybrid of adenocarcinoma and squamous cell lung cancer.  
  • Large cell neuroendocrine carcinoma is an aggressive form of NSCLC.  
  • Salivary gland-type lung carcinoma develops in the central airways of the lungs.  
  • Lung carcinoids are found in young patients.  
  • Mesothelioma develops in mesothelium tissue, which is thin tissue that lines the lungs and the abdomen. This type is linked to asbestos inhalation. 
  • Mediastinal tumors develop in the mediastinum, which is tissue that separates the lungs and the rest of the abdomen.  
  • Sarcomatoid carcinoma and malignant granular cell lung tumors are also forms of lung cancer that are extremely rare.  

If you are interested in reading more about the numerous types of lung cancer, check out these articles from the Cancer Treatment Centers of America, the American Lung Association, and Johns Hopkins.  

Signs and Symptoms 

Every individual will have different symptoms of lung cancer, and many individuals may not have any indicators that they are living with it. This list of symptoms comprises the most commonly reported symptoms associated with lung cancer. If you have any of these symptoms, it does not mean that you have this disease, but they are an indicator that you should schedule a screening for it.  

  • Persistent cough that may or may not worsen 
  • Coughing up blood or rust-colored mucous 
  • Chest pain that often increases when deep breathing, coughing, or laughing 
  • Hoarseness 
  • Appetite Loss 
  • Unexplained weight loss 
  • Shortness of breath 
  • Feeling weak or tired; persistent lethargy 
  • Persistent bouts of bronchitis or pneumonia  
  • Wheezing 

When lung cancer metastasizes to another portion of the body, the individual may experience: 

  • Bone pain in the back or the hip area 
  • Nervous systems abnormalities; headache, weakness/numbness of a limb 
  • Yellowing of the skin and/or eyes (in cases where it has spread to the liver) 
  • Swelling of the lymph nodes in the neck or collarbone 

Risk Factors  

Lung cancer has many risk factors that are, unfortunately, unable to be changed. On the bright side, however, there are many risk factors that are directly influenced by your behavior or environmental conditions you can manage.  

The unchangeable: 

  • Radiation therapy/exposure to the lungs. Individuals that have undergone radiation therapy due to other cancers in the chest area, such as breast cancer, are at an elevated risk for developing lung cancer. The same goes for those that have been treated with this treatment for Hodgkin disease. 
  • Air pollution is another risk factor. Researchers estimate that about 5% of worldwide deaths from lung cancer are associated with exposure to high rates of air pollution. If you live in an area with high rates of air pollution, such as larger cities, limit your exposure to it by limiting time spent in areas where it is high.  
  • Family history is another risk factor. If you have a blood relative that has been diagnosed, you may have an elevated risk. 
  • Personal medical history of lung cancer of course elevates your risk of developing it again. 

Prevention: The Changeable Risk Factors 

There are numerous preventable risk factors.  

  • Smoking is the leading risk factor for developing lung cancer, and roughly 80% of all lung cancer deaths are thought to be linked to smoking.  
  • Smoking marijuana, e-cigarettes, or vaping also increases your risk for developing lung cancer, as inhaling the chemicals and tar in smoking these substances is not beneficial to the lungs. 
  • Inhaling secondhand smoke also elevates your risk of developing lung cancer, particularly when you are exposed to it in high frequency. This is associated with about 7,000 lung cancer deaths each year. 
  • Radon exposure. Radon is a naturally occurring gas that is radioactive and comes from the breakdown of uranium in rocks and soil. It is unable to been seen, smelled, or tasted. This is the second leading cause of lung cancer after smoking and is the leading cause of lung cancer among those that do not smoke. Outdoors, radon exposure is low. The risk of radon exposure occurs when indoors, where it becomes more concentrated and accumulates in places like homes, schools, offices, etc. Test your home and common places you spend time indoors for their radon levels to ensure you are not inhaling more than the acceptable amount.  
  • Asbestos exposure is linked to mesothelioma, but also can have a role in the development of any form of lung cancer. Those that work with asbestos in mines, mills, textile plants, etc., are much more likely to die should they develop lung cancer. Be sure to avoid asbestos to limit your exposure.  
  • Exposure to carcinogens, or cancer-causing agents, can increase lung cancer risk. These include diesel exhaust, uranium, arsenic, beryllium, cadmium, silica, vinyl chloride, nickel compounds, coal products, mustard gas, and chloromethyl ethers.  
  • Taking beta carotene supplements also elevates the risk of developing lung cancer in individuals that smoke. Avoid taking these supplements if you are a smoker.  

Talking to your doctor is most necessary if you are at an increased risk of developing lung cancer and have those conversations with your loved ones about your family’s medical history to best understand your risks. If you experience any symptoms associated with lung cancer, talk to your primary care doctor about scheduling a screening today. If you do not have a primary care physician, still plan to schedule a screening to ensure you are not suffering from lung cancer. 


Lung cancer screenings are encouraged for those at high-risk of developing lung cancer. This includes older adults with a history of smoking that otherwise show no symptoms, as lung cancer can often be present with no symptoms. Individuals within this category are advised to complete a lung cancer screening yearly.  

Lung cancer screening is highly encouraged for those that are: 

  • Between 50 and 80 years old 
  • Current smokers or those who have in the last 15 years 
  • Have a 20 or more pack-year smoking history. You can calculate your pack-year smoking history by assessing how many packs a day you smoke/smoked for how many years. For instance, an individual that smoked one pack a day for 20 years has a 20 pack-year smoking history. In addition, individuals that smoked 2 packs a day for ten years also have a 20 pack-year smoking history.  

The screening technique used for assessing the presence of lung cancer is computerized tomography, or CT scans. In this scan, the individual lays in the CT machine as it scans the lungs to develop images of them for a doctor to assess. CT scans do involve radiation exposure as the machine captures the images via x-ray, so it is important to discuss with your doctor the risks associated with the test. The sooner lung cancer is detected, the more likely it is that it can be effectively treated. The images that the CT scan produce are so detailed that they can reveal even the smallest of abnormalities in the lungs, enabling early detection.