Definition and Overview

Lung cancer is the leading cause of cancer deaths in the world. It is caused by the uncontrolled growth and rapid division of abnormal cells resulting in the formation of malignant tumours. The condition is broadly classified into two main types based on the cancer cell’s appearance under a microscope: non-small cell lung cancer (NSCLC) and small cell lung cancer. NSCLC is more common accounting for up to 85% of all lung cancers.

The three most common types of NSCLC are adenocarcinoma, squamous cell carcinoma, and large-cell lung carcinoma. They share similar prognoses and are treated the same way. However, they have distinct histologic and clinical characteristics.

  • Adenocarcinoma of the lung - Accounts for 50% of NSCLCs and about 40% of all lung cancers. It commonly occurs in the bronchioles or smaller airways. The condition is more common in women than men and tends to grow more slowly.

  • Squamous non-small cell lung cancer - Accounts for up to 30% of NSCLCs. It commonly develops within the space where the trachea joins the larger bronchi. It is more common in men than in women.

  • Large-cell lung carcinoma (LCLC) - A relatively uncommon type that is responsible for 10-15% of all lung cancers. Large cell carcinomas, which are mostly found in the lungs’ outer regions, tend to grow and spread more rapidly than squamous cell carcinoma and adenocarcinoma.

Other less common NSCLC types are pleomorphic, salivary gland carcinoma, carcinoid tumour, and unclassified carcinoma.

Causes of Condition

Cancer develops when normal cells continuously grow and divide instead of undergoing apoptosis (the process of programmed cell death). Instead of following a natural cycle wherein they grow, divide, and die so they can be replaced, cells continue to grow and form a malignant tumour. In lung cancer, this process normally breaks down due to tobacco smoking and exposure to second-hand smoke.

Aside from cigarette smoke, other substances that can cause DNA damage include car exhaust fumes, arsenic, asbestos, air pollution, and marijuana.

Lung cancer is also associated with radiation therapy to the chest area. It can also be the result of certain genetic mutations that increase the risk of cancer.

Key Symptoms

In the early stages, lung cancer non-small cell is asymptomatic which hinders patients from getting immediate medical attention. In about 10% of cases, the condition is accidentally discovered when patients undergo chest radiograph for another disease.

Those who experience non-small cell lung cancer symptoms mostly complain of pulmonary problems, such as:

  • Shortness of breath

  • Chronic cough

  • Chest pain

  • Wheezing

Other symptoms may include:

  • Weight loss

  • Loss of appetite

  • Difficulty swallowing

  • Swelling of the face and neck

  • Drooping eyelids

Other symptoms can also be observed when cancer has spread to other parts of the body. Signs of metastatic non-small cell lung cancer include:

  • Bone pain and fracture, if cancer spreads to the bone

  • Nausea, extreme fatigue, and yellowing of the skin, if cancer spreads to the liver

  • Blurred or double vision, headaches, and seizures, if cancer spreads to the spinal cord or brain

Who to See and Types of Treatments Available

Patients showing symptoms mentioned above, particularly those who smoke, are advised to see their family doctor or a general physician for an initial assessment. Doctors will discuss their medical history, conduct a thorough physical exam, and listen to their lungs using a stethoscope. Any abnormalities observed in this stage will prompt doctors to order additional diagnostic tests that will help them rule out other medical conditions and make a definite diagnosis. These tests include:

  • Sputum test – A routine test used to confirm any lung-related disorder that ranges from an infection to lung cancer. The procedure is painless and involves getting sputum sample to look for bacteria or fungi that may be causing the patient’s symptoms.

  • Complete blood count

  • Thoracentesis – Commonly recommended to patients who are having difficulty breathing. This test involves removing fluid from the pleural space for laboratory testing.

  • Imaging tests, such as chest MRI, positron emission tomography (PET) scan, chest x-ray, and bone scan.

  • Biopsy – If lung cancer is suspected, a piece of tissue is removed from the lungs for examination under a microscope.

By combining all test results, doctors can confirm a lung cancer diagnosis and the stage of the disease. Non-small cell lung cancer staging is crucial in determining the best possible treatment method for the patient.

  • Stage I - Small, localised malignant tumour

  • Stage II - Cancer that has spread to nearby lymph nodes

  • Stage III - Cancer that has spread to nearby and distant lymph nodes

  • Stage IV - Cancer that has spread to other organs such as the liver or brain

Non-small cell lung cancer treatment varies depending on many factors including the patient’s overall health condition and age, the extent of the disease, and whether the patient has another medical condition.

Early or non-metastatic NSCLCs are treated with surgery in which the malignant tumour is removed along with a wide margin of surrounding tissue. Depending on the tumour’s size and location, surgeons may perform lobectomy (removal of one lobe), segmentectomy (removal of a segment of a lung lobe), or pneumonectomy (lung removal).

Chemotherapy is also an essential part of cancer treatment. When given after surgery, its goal is to kill remaining cancer cells. It can also be given before any surgical procedure to shrink the tumour so it can be safely removed. If surgery is no longer possible, such as in cases where the disease has spread to different parts of the body, chemotherapy and radiotherapy are combined mainly to relieve patient’s symptoms such as breathing problems and bone pain (if cancer has spread to the bone).

Non-small cell lung cancer prognosis is dependent on the stage of cancer. The five-year survival rate is 49% for patients with stage I lung cancer and only about 5% for those with metastatic cancer.


  • Ramalingham S, Pillai RN, Reinmuth N, Reck M. Chapter 44: First-line Systematic Therapy Options for Non-small Cell Lung Cancer. In: Pass HI, Ball D, Scagliotti GV, eds. The IASLC Multidisciplinary Approach to Thoracic Oncology. Aurora, CO: IASLC Press; 2014:583-605.

  • Safar AM, Spencer H, Su X, Coffey M, Cooney CA, Ratnasinghe LD, Hutchins LF, Fan CY (2005). "Methylation profiling of archived non-small cell lung cancer: a promising prognostic system". Clin. Cancer Res. 11 (12): 4400–5.

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