How do you diagnose lung cancer? Lung cancer is often suspected after an abnormal spot is found on a chest x-ray done to evaluate a cough or chest pain. During this frightening time, it is helpful to know some of the procedures that may be recommended to find out if the abnormality is benign (non-cancerous), or malignant (cancerous.) If the abnormality is malignant, further studies are done to see if the cancer has spread (metastasized) to other areas in the body.
History and Physical
When lung cancer is suspected, a physician will first perform a thorough history and physical exam. This is done to evaluate symptoms and risk factors for lung cancer, and to look for any physical signs suggestive of lung cancer. These can include abnormal lung sounds, enlarged lymph nodes
, or clubbing
of the fingernails (chubby fingernails.)
A chest x-ray is usually the first test performed to evaluate any concerns based on a careful history and physical. This may show a mass in the lungs or enlarged lymph nodes. Sometimes the chest x-ray is normal, and further tests are needed look for a suspected lung cancer. Even if a mass is found, these are not always cancerous and further studies are needed.
A CT scan is frequently the second step either to follow up on an abnormal chest x-ray finding, or to evaluate troublesome symptoms in those with a normal chest x-ray. CT scanning involves a series of x-rays that create a 3-dimensional view of the lungs. If the CT is abnormal, the diagnosis of lung cancer still needs confirmation through a sample of tissue by one of the procedures below.
In some patients, MRI will be used to evaluate the possibility of lung cancer. This procedure uses magnetism and does not involve radiation. Certain individuals, such as those with metal implants (pacemakers, etc) should not have MRI scans. The technician will ask questions to make sure these are not present.
A PET scan uses radioactive material to create colorful 3-dimensional images of a region of the body. This type of scan differs from the others in that it defines tumors that are actively growing. As an addition to the other procedures, some researchers suggest that PET scanning may detect tumors earlier, even before they are visible anatomically through other studies.
After a lung cancer is suspected based on imaging, a sample of tissue is required to confirm the diagnosis and determine the type of cancer. Sputum cytology is the easiest way to do this, but its use is limited to those tumors that extend into the airways. Sputum cytology is not always accurate and can miss some cancer cells.
In a bronchoscopy, a lung specialist inserts a tube into the airways to visualize and take a sample of the tumor. This procedure is used when the tumor is found in the large airways and can be reached by the scope. Patients are given anesthesia during this procedure to minimize discomfort.
With this procedure, a hollow needle is inserted through the chest wall, usually guided by CT visualization, to take a sample of the tumor. This can be performed for tumors that cannot be reached by bronchoscopy.
Endobronchial ultrasound is a relatively new technique for diagnosing lung cancer. During a bronchoscopy, physicians use an ultrasound probe within the airway to examine the lungs and area between the lungs (mediastinum.)
When lung cancer affects the periphery of the lungs, it can create a fluid build up between the lungs and the lung lining (pleural effusion
). With local anesthesia, a larger needle is inserted into the pleural space
from which either a diagnostic amount of fluid (small amount to test for cancer cells) or a therapeutic amount of fluid (large amount to improve pain/shortness of breath) is removed.
This procedure is done in the operating room under general anesthesia. A scope is inserted just above the sternum (the breast bone) into the region between the lungs to take tissue samples from lymph nodes.
Test to Determine Spread of Lung Cancer (Metastasis)
Lung cancer most commonly spreads to the liver
, the adrenal glands, the brain
, and the bones
. Common tests include:
- CT scan of the abdomen – to check for spread to the liver or adrenal glands
- CT scan of the brain – to look for metastases to the brain
- Bone Scan – to test for bone involvement, especially the back, hips and ribs
Other Tests During Diagnosis
Additional non-diagnostic tests are frequently performed during the diagnosis of lung cancer as well. These can include:
- Pulmonary function tests – these test lung capacity and can determine how much the tumor is interfering with breathing, and sometimes, whether it is safe to perform surgery
- Blood tests – certain blood tests can detect biochemical abnormalities caused by lung cancers, and can also suggest spread of the tumor
Chest X-Ray/Chest CT Terminology
At this time, it may also help to understand some of the terminology used by doctors to describe a "spot" on the lungs. A "lung nodule" is defined as an abnormality that is 3 cm (1 1/2 inches) in diameter or smaller. In contrast the term "lung mass" is used to describe an abnormal region on a imaging study of the chest that is greater than 3 cm in diameter.
National Institute of Health. Medline Plus: Lung Cancer. Updated 08/10/12. http://www.nlm.nih.gov/medlineplus/lungcancer.html