Tests Used to Diagnose Lung Cancer

by Elizabeth L Perkins

Posted on Wednesday 24th of August 2011

Evidence of lung cancer (LC) is often detected during a routine examination or while the doctor is taking x-rays to assess another condition. At that point, the disease is merely a suspicion. It must be diagnosed before a treatment path can be designed.

There are several methods used to diagnose lung cancer and determine whether it poses an immediate danger (i.e. whether it is malignant). In this article, we'll provide a brief overview of the most common tests used by pulmonologists and other doctors.

Lab Tests

Blood and urine tests are ordered to check for the presence of tumor markers. These are compounds released by cancerous tissue that can be found in blood and bodily fluids. The markers can only be used to form a tentative diagnosis of LC since they occasionally show up on test results when cancerous cells do not exist.

X-Rays Of The Chest

Chest x-rays display the lungs and other structures, and can show abnormal masses. They are useful in providing a quick and reasonably accurate view of the patient's lungs. However, like tumor markers in blood and urine, x-rays are fallible. They can display masses that are due to factors other than tumors.


Ultrasonography uses sound waves that bounce among the patient's organs, veins, and tissues. These sound waves produce an echo that is used by a computer to construct an image of the chest and lungs. This image can display abnormal masses that are likely to be tumors.

Computerized Tomography (CT) Scan

If chest x-rays, lab tests, and ultrasound produce a tentative diagnosis, the next test is a CT scan. This is usually done with a helical scanner that rotates around the body and generates a 3D image of the chest. While it is more accurate than the preceding tests, it is rarely conclusive.

Positron Emission Tomography (PET) Scan

During a PET scan, a doctor will inject a radioactive substance into the patient's body. This material can be tracked with a special camera that produces 3D images. The images display chemical activity taking place within the body. Areas with substantial activity suggest the presence of cancerous tumors.

Magnetic Resonance Imaging (MRI)

This is a test that uses radio waves and a magnet connected to a computer to construct accurate images of the target site (in this case, the lungs). Doctors can use these images to distinguish between tissue that is healthy and tissue that is diseased.

An MRI produces images that are more accurate than those produced by a CT scan. However, it is generally more expensive and requires more time.


During a bronchoscopy, the doctor will insert a bronchoscope - a thin, flexible tube - down the patient's main airways. This may be done through the mouth or nose. A small camera is fitted on the instrument to allow the doctor to inspect the airways and surrounding area. The purpose of this procedure is to retrieve a portion of an identified tumor for further examination.


A biopsy is usually necessary to form a firm diagnosis. This procedure is done to retrieve a tissue sample using a needle, an endoscope, or surgery. When using a needle, the doctor will insert it directly into the patient's chest. The extracted tissue sample is then sent to a pathologist for further testing. If the affected tissue cannot be reached with a needle, minor surgery is performed to access the lungs through small chest incisions.

Unless a physician is relatively certain that lung cancer exists, testing rarely begins with a biopsy or bronchoscopy. Instead, a preliminary diagnosis is formed before more accurate - and expensive - tests are ordered. There is an urgency to the testing, however, since the earlier a conclusive diagnosis can be made, the better the chances it can be treated successfully.

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