Diagnosis of Lung Cancer

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From A.P. Johnson Institute of Cancer Research

LUNG CANCER DIAGNOSIS


Early diagnosis of lung cancer is difficult because symptoms do not usually occur until the disease is more advanced. You may have felt well and your diagnosis came as a surprise to you and your doctor. Or, you may have had signs or symptoms of lung cancer during a routine physical examination, and your doctor ordered tests that found lung cancer. Certain tests need to be performed for a doctor to be able to diagnose lung cancer. Below is a description of some of the more common tests doctors use.

Chest X-Ray

A chest x-ray is the most common test used when lung cancer is suspected. It uses small amounts of radiation to take a picture of the inside of the chest, including the lungs. Tumors in your lungs can be seen on a chest x-ray. Your doctor may compare old chest x-rays with recent ones to see if the tumor is growing or shrinking.

Computed Tomography (CT) Scan

Computed tomography, also known as a CAT or CT scan, is another test used to help diagnose lung cancer. It’s similar to a chest x-ray but it gives a more detailed picture of the lungs. A CAT scan can detect extremely small tumors that may not be seen on a chest x-ray. Also, it may help your doctor determine whether or not the tumor has spread into the surrounding lymph nodes.

Magnetic Resonance Imaging (MRI), or MRI, is similar to a CAT scan, but it uses magnetic fields instead of radiation to create a picture. An MRI produces clear images of your internal body parts, including tissues, muscles, nerves, and bones. Your doctor can use these images to detect the presence of tumors.

Positron Emission Tomography (PET) Scan, or PET scan, determines the way the cells in the body act in the presence of sugar. Normal cells take in sugar and use it to make energy. Cancer cells usually take in more sugar than normal cells. If you are going to have a PET scan, your doctor will give you a special type of sugar before the test. The PET scan will detect the presence of tumors by detecting “hot spots,” which are bright colored areas on the picture where the sugar has been taken in by cells. The more sugar the tumor takes in, the more likely it is a cancer.

A special type of PET scan is available, which involves the use of a special sugar called fluoro-deoxyglucose (FDG). This PET scan is useful in evaluating the extent of your cancer. More FDG taken up by your lung tissues can mean a more advanced stage of cancer. A PET scan using FDG is more accurate in determining the stage of your cancer compared to a CAT scan.

Sputum Cytology

In this test, your sputum (or mucous that is coughed up) is collected and examined under the microscope to look for cancer cells. The most accurate way to do this test is to collect and analyze early morning mucus for three days.

Biopsy

The techniques that allow the doctor to view the inside of your body do not test the tumor for the presence of cancer cells. So, these tests do not provide absolute proof that you have cancer. To confirm the presence of cancer, a sample of tissue from the tumor is necessary. A biopsy is the removal and examination of a tissue sample from the tumor to determine if it is cancerous (malignant) or non-cancerous (benign). Biopsies can be obtained in several different ways depending on the location and the size of a tumor. Below are different ways a biopsy can be taken.