Lung cancer, also known as lung carcinoma, is defined as an uncontrolled growth of tumor cells in the lungs.
Lung cancer, also known as lung carcinoma, is defined as an uncontrolled growth of tumor cells in the lungs.

Lung cancer, also known as lung carcinoma, is defined as an uncontrolled growth of tumor cells in the lungs. The principal role of the lungs is to allow gaseous exchange between the air and blood and facilitate the availability of oxygen for cellular functions. Lung cancer can arise in any part of the lung, but 95 percent of cancers arise from the epithelial cells, which are lining the airways (bronchi and bronchioles). It is one of the most common causes of death due to cancer in both men and women throughout the world. The incidence of lung cancer escalated drastically after the increased usage of cigarette smoking.

The most common symptom of lung cancer is a cough that does not go away or worsens. Other symptoms are coughing up blood or rust-colored sputum (spit or phlegm) and chest pain. Lung cancer pain is often worse with deep breathing, coughing or laughing. Lung cancer can present with pain in the shoulders and back as well. Back pain could be generalized as a muscle ache or sharp pain.

What causes lung cancer?

The prevalence of lung cancer is mainly correlated with tobacco smoking. The continued exposure to the smoke damages the tissues of the lungs and makes it increasingly difficult to repair cells. The damaged cells begin to behave abnormally and start producing more damaged cells, leading to a mass or tumor formation. Also, exposure to radon (a naturally existing radioactive gas) has been identified as the second leading cause of lung cancer. Breathing in other hazardous substances, such as asbestos, over a long time can also cause lung cancer. Also, there is an increased risk of developing lung cancer in individuals who have inherited genetic mutations.

What are the types of lung cancer?

Lung cancers are broadly classified into two types based on the microscopic appearance of tumor cells. These two types of cancers grow, spread and are treated in different ways. The main types include

  1. Small cell lung cancers (SCLC) comprise about 10 to 15 percent of lung cancers. It is the most aggressive and rapidly growing of all types and is strongly related to cigarette smoking. SCLCs metastasize rapidly to many sites within the body and are mostly discovered after they have spread extensively.
  2. Non-small cell lung cancer (NSCLC) is the most common lung cancer, accounting for about 85 percent of all cases. NSCLC has three main types designated by the type of cells found in the tumor. They are
  • Adenocarcinomas: They are the most common type and start in the mucus-secreting gland cells in the lining of airways.
  • Squamous cell carcinoma: This develops in the flat, thin cells that cover the surface of the airways. It tends to grow near the center of the lung.
  • Large cell carcinoma: This is sometimes referred to as undifferentiated carcinomas. They are the least common type of NSCLC. The cancer cells appear large and round under the microscope.


Lung Cancer: Early Signs, Symptoms, Stages See Slideshow

What are the signs and symptoms of lung cancer?

Symptoms of non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) are almost the same. Early symptoms may include

Tumors at the top of the lungs can affect facial nerves, leading to drooping of one eyelid, pupil becoming smaller or lack of perspiration on one side of the face. Together, these symptoms are called Horner syndrome. It can also cause shoulder pain.

How is lung cancer diagnosed?

People with an increased risk of lung cancer may consider annual lung cancer screening using low dose computed tomography or CT scans. Lung cancer screening is generally offered to older adults who have smoked heavily (30 pack years, which is one pack per day for 30 years or two packs per day for 15 years), who currently smoke or who have quit smoking within the past 15 years. The tests preferred to rule out lung cancer includes

  • X-ray, computed tomography (CT) and magnetic resonance imaging
  • (MRI) scans
  • Sputum cytology
  • Biopsy
  • Mediastinoscopy
  • Positron emission tomography (PET)
  • Bone scans

How is lung cancer treated?

Treatment options include

  • Surgery to remove a part or all the lung.
  • Chemotherapy, which is a drug treatment that can kill cancer cells and shrink tumors.
  • Radiation therapy, which uses high-energy rays to kill cancerous cells.
  • Radio-frequency ablation, which uses a thin needle that is inserted and electric current is passed through it to destroy cancer cells.
  • Targeted therapy, which targets a specific cell behavior to prevent tumor growth.
  • Immunotherapy, which helps the body fight cancer cells.
  • Palliative therapy, which includes pain relief, oxygen therapy and other treatments to help manage symptoms and complications.


Lung cancer is a disease in which lung cells grow abnormally in an uncontrolled way. See Answer

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Medically Reviewed on 4/23/2021
Tan WW. Non-Small Cell Lung Cancer (NSCLC). Medscape.

Tan WW. Small Cell Lung Cancer (SCLC). Medscape.