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Lung cancer traditionally is categorized by the type of cell where it begins. Today, doctors can also diagnose the disease on a molecular level.
This approach usually looks for mutations in the DNA of cancer cells and/or proteins produced by the cells. There are hundreds of different molecular diagnoses, including mutations to the EGFR, ALK, KRAS and ROS1 genes.
These molecular subtypes can impact how quickly the disease grows and spreads. They also can predict how the disease will respond to specific treatments, including different types of chemotherapy, targeted therapy and immunotherapy. By diagnosing a patient’s disease on a molecular level, doctors can design treatment plans with the best chance of fighting each patient’s specific cancer.
The traditional diagnosis based on the type of cell where the cancer started can still help doctors understand the patient’s condition and make a treatment plan. The two main categories are:
Non-small cell lung cancer (NSCLC)
About 85% of lung cancer cases are considered NSCLC. It arises from the lungs’ epithelial cells, a type of cell that lines the surface of organs. There are several types of non-small cell lung cancer based on the type of epithelial cell where the disease begins, including adenocarcinoma, squamous cell carcinoma and large cell carcinoma.
Small cell lung cancer (SCLC)
About 15% of lung cancers are SCLC and almost always are caused by smoking tobacco. It often starts in the more central portions of the chest. It usually grows and spreads quickly to other parts of the body, including the lymph nodes. Because it is so aggressive, surgery is used less often for small cell lung cancer than non-small cell lung cancer.
When you breathe in, oxygen comes through your mouth and nose and then travels through the trachea, or windpipe. The trachea divides into two tubes called bronchi, which take the oxygen to the left and right lungs. Inside the lungs are smaller branches called bronchioles and alveoli, tiny air sacks where oxygen is transferred to the blood stream.
Each lung is divided into sections called lobes. The right lung has three lobes and the left lung has two lobes. The left lung is smaller than the right lung because the heart is also located in the left side of the chest. Each lobe can be further divided into bronchopulmonary segments.
The pleura is a thin membrane that covers the outside of each lung and lines the inside wall of the chest. The space between the lungs and the chest wall usually contains a very small amount of fluid that allows the lungs to move smoothly during breathing.
Cancer grows in lungs, may spread
When lung cancer is small and at an early stage, it usually does not cause symptoms. However, once the disease grows, it may damage surrounding tissue, interfering with the lungs’ normal function and causing symptoms such as hemoptysis (coughing up blood), shortness of breath or pain.
Lung cancer frequently spreads, or metastasizes through the lymphatic system. Lymph is a clear fluid that is drained from our tissues and contains immune cells that help fight infection. It travels through your body in lymphatic vessels. Lymph nodes are small, bean-shaped organs that link lymph vessels. They often trap cancer cells that have spread to the lymphatic system.
Cancer cells can spread to other parts of your body through the bloodstream, as well. When lung cancer spreads to other organs such as the liver or bone, it is known as stage IV lung cancer or metastatic lung cancer. Cancer that has spread to another organ is still referred to as lung cancer. Whether or not a lung cancer has spread to lymph nodes or to other organs significantly influences how the tumor is treated.
Sometimes, a tumor starts in another part of the body and then spreads, or metastasizes, to the lungs. These tumors are called lung metastases, and they are not the same as lung cancer. In these cases, they are the type of cancer where they came from. For example, a colon cancer with lung metastases is called metastatic colon cancer.
Lung cancer is the most common cause of cancer-related deaths and second most common cancer in both men and women in the United States. According to the National Cancer Institute, more than 230,000 people in the U.S. are diagnosed with the disease each year. While most cases are linked to tobacco smoking, a growing number of diagnoses are among non-smokers, especially among women. Most lung cancers are diagnosed after the disease has spread. As a result, the five-year survival rate for lung cancers is 22%, though cases that are caught before the disease has spread have a much higher survival rate.
A risk factor is anything that increases the chance that a person will develop a particular disease. The main risk factors for lung cancer are:
- A history of or current tobacco use
- Exposure to second-hand smoke
- Exposure to asbestos, arsenic, chromium or other chemicals
- Living in an area with air pollution
- A family history of lung cancer
- Infection with the human immunodeficiency virus (HIV)
- Radiation exposure, including radiation therapy to the breast or chest, and radon exposure. This is a minor risk factor and the benefits of radiation therapy as a cancer treatment far outweigh the risks.
In some cases, lung cancer can be passed down from one generation to the next. Genetic counseling may be right for you. Visit our family history site to learn more about genetic counseling and testing.
Frequently asked questions
Lung cancer is traditionally categorized by the type of cell where it begins. Small cell lung cancers (SCLCs) make up about 15% of lung cancers and almost always are caused by smoking tobacco. The cancer often starts in the more central portions of the chest — in the bronchi, the two large tubes that carry air from the windpipe to the lungs. It usually grows and spreads quickly to other parts of the body, including the lymph nodes. Because this cancer is so aggressive, surgery is used less often for SCLC than for non-small cell lung cancers.
Lung cancer stages are determined through various tests and procedures, including MRIs, CT scans, PET scans, and lymph node biopsies. The doctor will combine the results of these procedures to stage the cancer, using the TNM (tumor, node, metastasis) classification system.
Yes, you can get lung cancer from smoking. MD Anderson recommends lung cancer screening if you’re age 50–80, are a current smoker (or a former smoker who quit within the past 15 years), and have a 20 pack-year smoking history (for example, one pack a day for 20 years or two packs a day for 10 years).
Lung cancer is hereditary in some cases, and a family history of lung cancer is considered a risk factor. Some rare genetic conditions, such as Li-Fraumeni syndrome (LFS), are associated with an increased risk of developing lung cancer.
Lung cancer is sometimes curable; it depends on the specific cancer a person has and how early the cancer was caught. Some lung cancers are very aggressive, while others are very responsive to targeted therapy and are curable if caught early.
CT scans are used in certain instances, in combination with other tests, to help diagnose lung cancer. In the process of diagnosis, patients will typically undergo an imaging exam, usually a chest X-ray. Images alone are not enough to make a lung cancer diagnosis, but they can show areas of concern. If an image shows such an area, the doctor may order other scans, including a CT scan or a PET scan, to get additional details. If the findings of the image scans indicate cancer, the doctor will request the removal of tissue or fluid from the lung for examination. Obtaining a tissue or fluid sample is called a biopsy.
Why choose MD Anderson for your lung cancer treatment?
Choosing the right hospital may be the most important decision you can make as a lung cancer patient. At MD Anderson you’ll get treatment from one of the nation’s top-ranked cancer centers. Our expertise starts with the ability to accurately diagnose and stage even extremely rare cancers, then carries on through groundbreaking treatment and into survivorship.
As a patient at MD Anderson, you’ll see the benefits of care from a top-ranked cancer center. These include:
- Treatment from specialists who focus exclusively on lung cancer and other thoracic cancers, including radiation oncologists, medical oncologists, surgeons and pathologists.
- Molecular diagnosis of cancer cells, allowing doctors to identify which treatments have the best chance of success against your exact cancer.
- Expert surgical care designed to offer complete resection of your tumor and any involved lymph nodes.
- An enhanced surgical recovery program along with robotic and minimally invasive procedures that offer faster recovery times and less pain from surgery.
- Groundbreaking clinical trials that may not be available anywhere else. These include trials of new targeted therapies, immunotherapies and drug combinations.
MD Anderson patients also have access to all the services and support offered by one of the nation’s top-ranked comprehensive cancer centers. From counseling and support groups to integrative medicine and physical therapy, MD Anderson has all the support and wellness services needed to treat the whole person – not just the disease.
This support and care is available beyond MD Anderson’s campus in the Texas Medical Center. Through our Houston-area locations, patients throughout the region can get top-ranked care and personalized attention close to home.
They're focused on you as a person, and they're focused on fighting the disease. But they also show so much kindness and compassion.
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Prevention & Screening
Many cancers can be prevented with lifestyle changes and regular screening.