Cancer is an out-of-control growth of abnormal cells. Cancer cells have abnormal DNA (deoxyribo-nucleic acid)-the genetic information in all the cells of the body that determines individual hereditary characteristics. DNA can be abnormal from inheriting damaged DNA or from being damaged from environmental exposure.
Cancer cells usually form a tumor, which is an abnormal growth of tissue. Some cancers like leukemia involve blood and blood-forming organs. This is a problem because normal tissue is replaced with the cancerous tissue, and the organ does not function properly. Cancer cells can travel to other parts of the body by the lymph system, and begin to grow. This process of spreading in the body is called metastasis.
Types of Lung Cancer
A pathologist is a doctor who studies diseases by looking at tissue and cells under a microscope. The pathologist can tell what type of cancer cells are in the tissue. There are two main types of lung cancer; small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC).
About 13% of lung cancers are small cell. The other 87% that are non-small cell are divided into subgroups: squamous cell carcinoma, adenocarcinoma, and large cell undifferentiated carcinoma.
Chest Anatomy and Physiology
In order to understand some things about lung cancer, let's review what organs are in your chest.
The chest contains a trachea, commonly called windpipe, which carries air to the lungs. It has two main branches. Each branch of the trachea is called a bronchus. These two branches connect to your lungs. Each bronchus continues to divide into smaller branches and tiny air sacs called alveoli.
We have two lungs, which are divided into sections called lobes. Your right lung is divided into three lobes: upper, middle, and lower. Your left lung is divided into two lobes: upper and lower. You also have a large muscle that divides your chest from the abdomen called the diaphragm. The lungs are surrounded by a tissue lining called the pleura.
The chest also contains your heart and aorta (main artery that carries blood to the heart), as well as other blood vessels and nerves. All these organs are protected by the rib cage and breastbone, also known as the sternum.
Throughout our body we have a lymphatic system, which is part of our circulatory (blood) system. In the chest and other parts of the body, we have lymph nodes-pea-sized "glands" that filter impurities from the body. You may hear different terms used to describe their locations in the chest, such as mediastinal (area between pleural sacs), hilar (area near opening through which bronchus, blood vessels, and nerves pass), or paratracheal (area near trachea).
Diagnostic Tests
Many diagnostic tests may be ordered to evaluate whether you have lung cancer, the "stage" it is at if you do have it, and the condition of your lungs and/or heart. Here is a list of some commonly ordered tests:
- Chest X-Ray: A chest x-ray (CXR) is an x-ray image of the chest, lungs, heart, large arteries, ribs, and diaphragm. It looks like the negative of a photograph. This test is performed in our hospital's radiology department. Two views are usually taken: one in which the x-rays pass through the chest from the back (posterior-anterior view), and one in which the x-rays pass through the chest from one side to the other (lateral view). You stand in front of the x-ray machine, and must hold your breath when the x-ray is taken.
- CT Scan: Computed tomography, also called computerized axial tomography (CAT), is an x-ray imaging technique that produces pictures of slices or cross-sections through the body. It is used to tell the size of a tumor, whether the lymph nodes (see above) are enlarged, or whether other organs of the body are affected. For more information, please click here.
- MRI: Magnetic resonance imaging uses of a strong magnet and radio waves to make images of the body. It is often useful to see if cancer has spread (metastasized) to the brain. For more information, please click here.
- PET Scan: Positron emission tomography is an imaging technique in which a form of sugar with a radioactive tracer is injected into the patient, and then a special camera takes pictures. Cells that are highly metabolic, such as cancer cells, take up this sugar and show up as "hot spots." These images are useful in providing an indication of whether the tumor is cancerous or whether the lymph nodes (see above) are involved. For more information, please click here.
- Pulmonary Function Test: This test (also known as PFT) is a breathing test that measures how well your lungs are working. For more information, please click here.
- Cardio-Pulmonary Exercise Test: This test (also known as CPET) is performed to evaluate your lung function in relationship to your heart. For more information, please click here.
- Cardiac Stress Test: This test is performed to evaluate the condition of your heart. You may be asked to do the form of the test in which you run on a treadmill; or the form in which a medication is given to you through an IV line (intra-venous; into a vein), after which special x-rays are often taken of your heart. For more information, please click here.
Biopsy Techniques
A biopsy refers to the removal and examination of tissue and cells from a tumor or lymph node. This test is used to help make a diagnosis of lung cancer, as well as to determine the "stage" of possible cancer. The sample of tissue or cells taken for a biopsy is sent to the pathologist who evaluates it. There are a few different ways to perform a biopsy.
Here are techniques that we use:
- Bronchoscopy: A pulmonologist (lung specialist) uses an endoscope (a device that consists of a tube and an optical system) to look down your bronchus and take tissue samples. For more information, please click here.
- Mediastinoscopy: A surgeon makes a small incision just above your breastbone and uses a scope to look under your breastbone to take tissue samples. For more information, please click here.
- Thoracoscopy: A surgeon makes three small incisions on the side of your chest between your ribs, and uses a scope to look at the lung and pleural spaces. Tissue samples are then taken. This kind a procedure requires a stay in the hospital. For more information, please click here.
- Fine-Needle Aspiration: A very thin needle attached to a syringe is inserted into a tumor to withdraw a small amount of cells. Many times an ultrasound or CT scan is used to help guide the needle to penetrate the tumor. Unfortunately, fine-needle aspiration is sometimes "non-diagnostic", does not provide the information requires to make a diagnosis. A negative result even may not be accurate when it indicates there is no cancer, since there is a chance the needle could miss the tumor. For more information, please click here.