Diagnosis

Doctors use many tests to diagnose cancer and determine if it has spread from the lung. Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible or more information is needed, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized, but they can never be used to diagnose lung cancer. Only a biopsy can do that. Your doctor may consider these factors when choosing a diagnostic test:

• Location of the suspected cancer
  
  
• Size of the suspected cancer
  
  
• Age and medical condition
  
  
• The type of cancer suspected
  
  
• Severity of symptoms
  
  
• Previous test results

In addition to a physical examination, the following tests may be used to diagnose lung cancer:

Biopsy. A biopsy is the only way to make a diagnosis of lung cancer. A biopsy is the removal of a small amount of tissue for examination under a microscope. The sample removed from the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). If cancer cells are present, the pathologist will determine if it is small cell lung cancer or NSCLC, based on its appearance under the microscope.

Common procedures doctors use to obtain tissue for the diagnosis and staging of lung cancer are listed below:

Sputum cytology. If there is reason to suspect lung cancer, the doctor may ask a person to cough up some phlegm so it can be examined under the microscope. A pathologist can find cancer cells mixed in with the mucus.

Bronchoscopy. In this procedure, the doctor passes a thin, flexible tube with a light on the end into the mouth or nose, down through the main windpipe, and into the breathing passages of the lungs. A surgeon or a pulmonologist (a medical doctor who specializes in the diagnosis and treatment of lung disease) may perform this procedure. The tube lets the doctor see inside the lungs. Tiny tools inside the tube can take samples of fluid or tissue, so the pathologist can examine them. Patients are given mild anesthesia (medication to put them to sleep) during a bronchoscopy.

Needle aspiration. After numbing the skin, a special type of radiologist, called an interventional radiologist, inserts a small needle through the chest and directly into the lung tumor. The doctor uses the needle to aspirate (suck out) a small sample of tissue for testing. Often, the radiologist uses a chest CT scan or special x-ray machine called a fluoroscope to guide the needle.

Bone marrow biopsy. For patients with small cell lung cancer, doctors sometimes use a local anesthetic (to numb the area) and a special needle to remove a tiny piece of bone (typically from the hip bone) in order to determine whether small cell cancer is present within the bones.

Thoracentesis. After numbing the area, a needle is inserted through the chest wall and into the space between the lung and the wall of the chest where fluid can collect. The fluid is removed and checked for cancer cells by the pathologist.

Thoracotomy. This procedure is performed in an operating room with the help of general anesthesia. A surgeon then makes an incision in the chest, examines the lung directly, and takes tissue samples for testing. A thoracotomy is the procedure surgeons most often perform to completely remove a lung tumor.

Thoracoscopy. Through a small cut in the skin of the chest wall, a surgeon can insert a special instrument and a small video camera to assist in the examination of the inside of the chest. Patients require general anesthesia, but recovery time may be shorter given the smaller incisions. This procedure may be referred to as “VATS” (video-assisted thoracoscopic surgery).

Mediastinoscopy. A surgeon examines and takes a sample of the lymph glands in the center of the chest (underneath the breastbone) by making a small incision at the top of the breastbone. This procedure also requires general anesthesia and is done in an operating room.

Imaging tests

In addition to biopsies and surgical procedures, imaging scans are vital to the care of people with lung cancer. However, no test is perfect, and no scan can diagnose lung cancer. Only a biopsy can do that. Chest x-ray and scan results must be combined with a person’s medical history, a physical examination, blood tests, and biopsy information to form a complete story about where the cancer began and whether or where it has spread.

CT scan. This test produces images that allow doctors to see the size and location of lung tumors and/or lung cancer metastases.

Magnetic resonance imaging (MRI) scan. This test also produces images that allow doctors to see the size and location of lung tumors and/or lung cancer metastases. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium (a special dye) may be injected into a patient’s vein to provide better detail. MRI scanning is imprecise when used to image a structure that is moving, like your lungs, which move with each breath a person takes. For that reason, the MRI scan is rarely used to study the lungs themselves.

Scans are also available that use radioactive molecules, called tracers, injected into the blood to show where cancer is possibly located:

Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. This substance gives off energy that is detected by a scanner, which produces the images. A specialist in nuclear medicine helps your doctor interpret PET scans.

Bone scan. A bone scan uses a radioactive tracer to look at the inside of the bones. The tracer is injected into a patient’s vein. It collects in areas of the bone and is detected by a special camera. Healthy bone appears gray to the camera, and areas of injury, such as those caused by cancer, appear dark.

Bone scans and PET scans are often used in combination with information gathered from a CT scan, MRI, regular x-rays, and a physical examination.

To learn more about what to expect during common diagnostic tests, read Cancer.Net: Tests and Procedures.

Finding out where the cancer started

Lung cancer starts in the lungs. Many other types of cancer start elsewhere in the body and spread to the lungs when they metastasize. For example, breast cancer that has spread to the lungs is still called breast cancer. Therefore, it is important for doctors to know if cancer started in the lungs or elsewhere.

To find where the cancer started, the doctor takes into account the patient’s symptoms and medical history, physical examination, the appearance of the tumor on x-rays and scans, and risk factors for cancer. A pathologist can perform tests on the biopsy sample to help identify the origin of a cancer, and the doctor may order other tests for the patient to rule out specific types of cancer. If, after these considerations, the doctor is still not sure where the cancer started, the doctor may give a diagnosis of metastatic cancer “of unknown primary.” Most treatments for metastatic cancer of unknown primary that are first discovered in the chest are the same as those for metastatic lung cancer.

To learn about the terms used in this section, read the Cancer.Net Feature: Cancer Terms to Know: Newly Diagnosed.