What is lung cancer?

What is lung cancer?

Like other cancers, lung cancer develops when normal processes of cell division and growth are disrupted, giving way to abnormal, uncontrollable growth. The cells grow into a mass, or tumor. Any abnormal growth in the body that directly invades surrounding tissues and organs, spreads to other parts of the body, or has the potential to grow back after being removed is called “malignant,” or cancerous.

Who gets lung cancer?

Lung cancer can take several years to develop. Cigarette smoking is the most common risk factor for developing lung cancer. Many people exposed to cigarette smoke – or some of its components – will end up with permanent abnormal changes in their lungs. These changes can cause a cancerous tumor to develop within the lung.

  • Twenty-five percent of all cases of lung cancer worldwide are diagnosed in people who have never smoked. The underlying cause in these cases is not well understood.
  • Two out of three people diagnosed with lung cancer are over age 65.
  • The most common age at diagnosis is 70 years.

How common is lung cancer?

Lung cancer is the second most common malignancy in the country, but it is the deadliest as it causes the highest number of deaths of all cancers. Lung cancer diagnoses are expected to be about 228,150 new cases in 2019 in the United States, while a predicted 142,670 deaths will occur in 2019.

What are the stages of lung cancer?

Staging allows the physician to fully understand the extent of the patient’s cancer to determine treatment decisions and predict expected outcomes. Doctors use specific terms to describe the stages of cancer, but a straightforward way of describing staging might be as follows:

  • Localized : The cancer is confined to the lung.
  • Regional : The cancer has spread to lymph nodes (or glands) within the chest.
  • Distant :The cancer has spread (or metastasized) to other parts of the body.

What are the types of lung cancer?

Most lung cancers start in the lining of the bronchi (air passageways branching off the trachea, or breathing tube). Lung cancer also can form in glands below the lining of the bronchi, frequently in the outer areas of the lungs. These lung cancers are one of two major types, small cell or non-small cell lung cancer, each of which grows and spreads different ways:

Non-small cell lung cancer

Non-small cell lung cancer is much more common, and usually grows and spreads more slowly than small cell lung cancer. There are three main types of non-small cell lung cancer, named for the type of cells from which the cancer develops:

  1. Adenocarcinoma often starts growing near the periphery of the lung and may vary in both size and growth rate. This is the most common type of lung cancer in both smokers and those who have never smoked.
  2. Squamous cell carcinoma usually starts in one of the larger breathing tubes near the center of the chest. The size of these lung tumors can range from very small to quite large.
  3. Large cell carcinoma often starts near the periphery of the lung, grows rapidly and is usually quite extensive when diagnosed.
Small cell lung cancer

Small cell lung cancer is less common than non-small cell lung cancer accounting for about 15 percent of all lung cancers. This type of lung cancer grows rapidly, is likely to be advanced by the time of diagnosis and spreads to other parts of the body quickly.

Rare cancers of the chest

There are more than a dozen kinds of uncommon tumors that can develop in the chest, which may or may not arise from the lung. Some of the less common types include carcinoid tumors (often located in a large airway), and malignant mesothelioma that develops from the pleura, or lining of the lung.


Mesothelioma is a cancer that affects the mesothelium, the protective membrane that covers most of the body’s internal organs. This rare cancer affects only about 3,000 people annually, usually in the part of the mesothelium surrounding the lungs (pleura) but sometimes in the pericardium that covers the heart. Mesothelioma typically happens decades after exposure to asbestos.

What are symptoms of lung cancer?

Signs and symptoms of lung cancer are not always present until the disease advances. However, some people do have symptoms early. These include:

  • Coughing that does not improve
  • Hoarseness
  • Blood in phlegm or sputum that is expelled by coughing
  • Weakness
  • Wheezing
  • Infections that return or will not clear
  • Chest pain that gets worse with cough or laugh

Advanced lung cancer symptoms include coughing, shortness of breath, chest pain, fatigue and/or unintentional weight loss. Signs and symptoms that might appear if the cancer has spread to other places include bone pain, headache, muscle weakness and/or eyelid drooping.