Lung Cancer: The Basics

Christopher Dolinsky, MD and Christine Hill-Kayser, MD
The University of Pennsylvania Medical School
Last Modified: December 10, 2013

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Lung cancer happens when cells in the lung begin to grow out of control. Large collections of cancer cells are called tumors. Lung cancer is not a single disease, but rather a collection of several diseases that are characterized by the affected cell type. Lung cancer is divided into two main categories:

  • Small Cell Lung Cancer (SCLC): accounts for about 15% of all lung cancers. SCLC is more aggressive than non-small cell lung cancer because it grows more quickly and is more likely to spread to other organs.
  • Non-Small Cell Lung Cancer (NSCLC): accounts for 85% of all lung cancers. NSCLC is generally slower growing than small cell lung cancer and is divided into different types based on the cells that make up the tumor, including adenocarcinoma, squamous cell carcinoma, and poorly differentiated or large cell carcinoma.

The lungs can also be affected by cancer that has spread from another part of the body, called metastatic cancer. Two other types of cancer that can affect the lungs are mesothelioma, which affects the lining of the lung or abdomen, and carcinoid tumors, which can occur in the lung. These cancers will not be discussed in this article.

Risk Factors

Smoking tobacco (currently or in the past), is the leading cause of lung cancer. However, the number of cases in non-smokers has been increasing in recent years. Other risk factors for lung cancer include exposure to radon, radiation, asbestos, and environmental pollution.


Research has found that people who are current or former heavy smokers who have a special type of CT scan done to screen for lung cancer have lung cancer detected in earlier stages and have improved survival. Speak to your healthcare provider to determine if this screening test is right for you.

Signs & Symptoms of Lung Cancer

Unfortunately, the early stages of lung cancer may not have any symptoms. As the tumor grows in size, it can produce a variety of symptoms including:

  • Cough (especially one that doesn't go away or gets worse in character)
  • Chest pain
  • Shortness of breath
  • Coughing up blood or bloody phlegm
  • New onset hoarseness or wheezing
  • Recurrent problems with pneumonia or bronchitis
  • Weight loss
  • Loss of appetite
  • Fatigue
  • Bone pain
  • Dizziness or double vision
  • Hoarseness of change in speech
  • Numbness or tingling in your arms or legs
  • Arm pain or weakness
  • Neck or facial swelling
  • Yellowing of the skin or whites of the eyes (jaundice)
  • Seizures

Many of these symptoms could be caused by a variety of problems; however, your healthcare provider needs to see you if you have any of these problems. A cough is the most common presenting symptom of lung cancer; however, many long-term smokers have a chronic cough, so it is especially important for someone with a chronic cough to see their doctor if their cough changes in character or severity.

Diagnosing Lung Cancer

When your healthcare provider is suspicious of a lung tumor, they may order tests to further investigate, including:

  • Chest x-ray
  • CT scan (a 3-D x-ray)
  • Sputum cytology, which means examining your phlegm for cancer cells.
  • If these tests locate a concerning area, you may have additional testing, including a PET scan and an MRI scan of the brain to further evaluate the lesion or mass and to evaluate other areas of the body where lung cancer typically spreads.

While all of these tests are important pieces of the puzzle, a biopsy is the only way to know for sure if you have cancer. A biopsy takes a sample of the suspicious area, which is examined under a microscope for the presence of cancer cells. The biopsy also determines the type of lung cancer and if there are cancer cells present in the lymph nodes. The biopsy may be done using a brochoscopy (small camera passed down your throat into the lungs) or by a surgical procedure.

A pathology report is sent to your healthcare provider, detailing if the specimen is cancer or not; and if it is cancerous, what type of tissue it arose from, what subtype of lung cancer it is, how abnormal it looks (known as the grade), and whether or not it is invading surrounding tissues. This is an important piece in planning your treatment. You can request a copy of your report for your records.

Staging Lung Cancer

In order to guide treatment and offer some insight into prognosis, lung cancer is "staged." This stage is based on the size and location of the tumor, if there are cancer cells in the lymph nodes and if there are cancer cells found in other areas of the body.
Stages range from stage I (smallest, most confined tumors) to stage IV (tumors that have spread to other areas of the body). The stage and type of lung cancer will guide your treatment recommendations.

Treatment of Lung Cancer

In general, the following treatments are used:

  • "Early Stage" (stages I, II and some III cancers): Surgery is used in patients who can tolerate the procedure. Most patients will also receive chemotherapy either before surgery (called neoadjuvant) or after surgery (called adjuvant). Radiation therapy can be given in patients who are not optimal candidates for surgery. With radiation therapy, most patients will also receive chemotherapy, either given before radiotherapy or during radiotherapy.
  • "Locally Advanced" (stages IIIA and some IIIB): Chemotherapy given before or during radiation therapy. Select patients can also be considered for surgery, almost always in combination with radiation therapy and chemotherapy.
  • "Advanced" (stage IIIB and IV): Chemotherapy is used to prolong survival and improve quality of life. Molecular testing is often used to determine the appropriateness of certain targeted therapies for treatment.

This article is a basic introduction to lung cancer. You can learn more about your specific type of lung cancer and it’s treatment by using the links below.

All About Non-Small Cell Lung Cancer

All About Small Cell Lung Cancer

All About Mesothelioma

Lung Cancer Web-U-Cation Program: This video will help you learn about lung cancer, its diagnosis, staging, potential treatments and side effects. In addition, it will address coping with cancer (practical, emotional & family issues), coping with the stigma of lung cancer, and concerns surrounding work, insurance and disability.


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