Lung cancer

Lung cancer is a type of cancer that begins in the lungs. Your lungs are two spongy organs in your chest that take in oxygen when you inhale and release carbon dioxide when you exhale. Lung cancer is the leading cause of cancer deaths worldwide.

People who smoke have the greatest risk of lung cancer, though lung cancer can also occur in people who have never smoked. The risk of lung cancer increases with the length of time and number of cigarettes you've smoked. If you quit smoking, even after smoking for many years, you can significantly reduce your chances of developing lung cancer.

Symptoms

Lung cancer typically doesn't cause signs and symptoms in its earliest stages. Signs and symptoms of lung cancer typically occur when the disease is advanced.

Signs and symptoms of lung cancer may include:

  • A new cough that doesn't go away
  • Coughing up blood, even a small amount
  • Shortness of breath
  • Chest pain
  • Hoarseness
  • Losing weight without trying
  • Bone pain
  • Headache

Causes

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.

How smoking causes lung cancer

Doctors believe smoking causes lung cancer by damaging the cells that line the lungs. When you inhale cigarette smoke, which is full of cancer-causing substances (carcinogens), changes in the lung tissue begin almost immediately. At first your body may be able to repair this damage. But with each repeated exposure, normal cells that line your lungs are increasingly damaged. Over time, the damage causes cells to act abnormally and eventually cancer may develop.

Types of lung cancer

Doctors divide lung cancer into two major types based on the appearance of lung cancer cells under the microscope. Your doctor makes treatment decisions based on which major type of lung cancer you have.

The two general types of lung cancer include:

  • Small cell lung cancer
  • Non-small cell lung cancer

Risk factors

A number of factors may increase your risk of lung cancer. Some risk factors can be controlled, for instance, by quitting smoking. And other factors can't be controlled, such as your family history.

Risk factors for lung cancer include:

  • Smoking
  • Exposure to secondhand smoke
  • Previous radiation therapy
  • Exposure to radon gas
  • Exposure to asbestos and other carcinogens
  • Family history of lung cancer

Complications

Lung cancer can cause complications, such as:

  • Shortness of breath
  • Coughing up blood
  • Pain
  • Fluid in the chest (pleural effusion) 
  • Cancer that spreads to other parts of the body (metastasis)

Prevention

There's no sure way to prevent lung cancer, but you can reduce your risk if you:

  • Don't smoke. If you've never smoked, don't start. Talk to your children about not smoking so that they can understand how to avoid this major risk factor for lung cancer.
  • Stop smoking.
  • Avoid secondhand smoke.
  • Test your home for radon.
  • Avoid carcinogens at work.
  • Eat a diet full of fruits and vegetables.
  • Exercise most days of the week.

https://www.mayoclinic.org/diseases-conditions/lung-cancer/symptoms-causes/syc-20374620