How Lung Cancer Is Diagnosed

Lung cancer is often suspected after an abnormal spot is found on a chest X-ray done to evaluate a cough or chest pain. But since this test can miss early cancers, additional testing is needed to confirm (or rule out) a lung cancer diagnosis. This can include a chest computed tomography (CT) scan and, if a nodule or mass is found, a biopsy.

It's helpful to know more about some of the procedures that may be recommended to find out if an abnormality is benign (non-cancerous) or malignant (cancerous). If the latter, further studies are done to see if the cancer has spread (metastasized) to other areas in the body and to figure out the stage of the disease.

Screening

It's important to catch lung cancer as early as possible. Some cases may first be detected during lung cancer screenings, which are performed on individuals who don't have any symptoms and meet the following criteria:

  • Are between the ages of 55 and 80
  • Smoke or smoked for a total of 30 pack-years
  • Continue to smoke or quit smoking in the past 15 years

Knowing your risk factors for lung cancer and getting screened when appropriate can lead to earlier detection, diagnosis, and treatment. Talk to your doctor about whether lung cancer screening would be beneficial and appropriate for you.

If you have any possible symptoms of lung cancer, such as a persistent cough, shortness of breath, or unexplained weight loss, further tests will be needed.

Physical Examination

When lung cancer is suspected, a physician will 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 the disease.

These can include:

  • Abnormal lung sounds
  • Enlarged lymph nodes
  • Unintentional weight loss
  • Clubbing of the fingernails (chubby fingernails)

Imaging

A number of different imaging studies may be needed, depending on your specific symptoms and findings on exam. These may include:

Chest X-Ray

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 to look for a suspected lung cancer. Even if a mass is found, it may not be cancerous, and further studies are required to confirm its status.

Chest X-ray alone is not sufficient to rule out lung cancer, and early cancers can easily be missed with these tests. In fact, about 90% of missed lung cancer diagnoses are due to a reliance on chest X-ray.

Nodules vs. Masses

A lung nodule is considered a spot on the lung that is 3 centimeters (1.5 inches) or less in diameter. A lung mass refers to an abnormality that is larger than 3 centimeters in diameter.

A spot on the lung, a lung lesion, could be benign or malignant. A shadow on an X-ray could be a sign of either as well, or simply represent the overlapping of normal structures in the chest.

CT Scan

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 three-dimensional view of the lungs. If the CT is abnormal, the diagnosis of lung cancer still needs confirmation through examination of a sample of lung tissue.

MRI

For some people, magnetic resonance imaging (MRI) will be used to evaluate the possibility of lung cancer. This procedure uses magnetism without radiation.

Certain individuals, such as those with metal implants (e.g., pacemakers) should not have MRI scans. The technician will ask questions to make sure these are not present.

PET Scan

A positron emission tomography (PET scan) uses radioactive material to create colorful three-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.

A small amount of radioactive sugar is injected into the bloodstream and given time to be taken up by cells. Cells that are actively growing take up more sugar and light up on films. The test is usually combined with a CT scan (PET/CT).

Some researchers suggest that PET scanning may detect tumors earlier on, even before they are visible through other studies. PET scans are also useful for distinguishing between tumors and scar tissue in people who have scarring in their lungs for any reason.

Lung Biopsy

If lung cancer is suspected on imaging studies, the next step is to have a lung biopsy done to determine whether or not the abnormality is truly cancer and to determine the type of lung cancer. The biopsy material can be obtained via bronchoscopy, endobronchial ultrasound, fine needle aspiration, thoracentesis, or mediastinoscopy.

When lung cancer spreads, it's important to "re-biopsy" tissue, as cancers can change in time and these changes can, in turn, help you and your doctor choose the best treatment options.

Bronchoscopy 

In a bronchoscopy, a lung specialist inserts a tube with a scope into the airways to visualize a tumor. A biopsy of any tumor or other abnormalities that are seen may be taken during this procedure.

Bronchoscopy is only used when the tumor is found in the large airways and can be reached using these instruments. Patients are given anesthesia to minimize discomfort.

Endobronchial Ultrasound

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). For tumors that relatively close to the airways, a biopsy may be done with this imaging.

Fine Needle Biopsy

In a fine needle aspiration (FNA) biopsy, a physician inserts a hollow needle through the chest wall, usually guided by CT visualization, to take a sample of the tumor.

This can be performed for tumors that can't be reached by bronchoscopy, especially those that are near the periphery of the lungs.

Thoracentesis

When lung cancer affects the periphery of the lungs, it can cause fluid to build up between the lungs and the lung lining (pleura). With local anesthesia, a larger needle is inserted into the pleural cavity from which either a diagnostic amount of fluid (small amount to test for cancer cells, a malignant pleural effusion) or a therapeutic amount of fluid (large amount to improve pain and/or shortness of breath) is removed.

Mediastinoscopy

A mediastinoscopy 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 (mediastinum) to take tissue samples from lymph nodes.

A PET scan can now often provide the same results that a mediastinoscopy did in the past.

Labs and Tests

Non-diagnostic tests are frequently performed during the diagnosis of lung cancer as well. These can include:

  • Pulmonary function tests (PFTs): These test lung capacity and can determine how much a tumor is interfering with breathing and, sometimes, whether it's 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.

Sputum Cytology

Sputum cytology is the easiest way to confirm the diagnosis and determine the type of lung cancer, but its use is limited to those tumors that extend into the airways.

Sputum cytology isn't always accurate and can miss some cancer cells. The test is of most benefit when positive, but says little if it's negative.

Molecular Profiling/Gene Testing

It's now recommended that everyone with non-small cell lung cancer—and especially lung adenocarcinoma—have molecular profiling done on their tumor. This does not diagnose the cancer, but instead confirms characteristics that can help tailor treatment—namely, mutations in cancer cells for which targeted medications are available.

These aren't mutations that you're born with, nor can you pass them on to your children. They're mutations that occur in the process of a cell becoming cancerous that "drive" the growth of cancer.

Targeted treatments are currently approved for people with EGFR mutations, ALK rearrangementsROS1 rearrangements, and a few other mutations. In addition, other treatments are currently being studied in clinical trials.

What Is a Liquid Biopsy?

Most biopsies are done on tissue samples, but liquid biopsies are an exciting new way to follow some people with lung cancer. Approved in June of 2016, these tests can be done via a simple blood draw.

Currently, they're approved only for detecting EGFR mutations, but they're a good example of how the diagnosis and treatment of lung cancer is improving every year.

PD-L1 Testing

PD-L1 is a protein that's expressed in greater amounts on some lung cancer cells. This protein serves to enhance the "brakes" of the immune system, reducing its ability to fight off cancer cells. Some cancer cells have found ways to "overexpress" this protein as a method of hiding from the immune system. Medications known as checkpoint inhibitors work by blocking this action and essentially releasing the brakes on the immune system.

Since the first immunotherapy drug was approved for the treatment of lung cancer in 2015, three additional medications have become available. A PD-L1 test may be done to determine the percent of expression of PD-L1 on your cancer cells which, here too, can help further define the characteristics of your tumor and help guide treatment.

Still, the test's utility is not fully understood. Both lung cancers that overexpress PD-L1 and those that don't may respond to these drugs. Currently, it's thought that such testing may be cost-effective, but limiting the use of these drugs only to people who have tumors that overexpress PD-L1 could reduce the number of people who would benefit from these treatments.

Identifying Type and Stage

Cytology testing performed on biopsy samples can determine both whether lung cancer is present and the type of cancer, if present.

There are two primary types of lung cancer:

Non-small cell lung cancer is most common, accounting for 80% to 85% of lung cancer diagnoses. Non-small cell lung cancer is further broken down into three types:

  • Lung adenocarcinoma is the most common type of lung cancer in the U.S. today, responsible for 40% of all lung cancers. It's the most common type of lung cancer found in women, young adults, and in people who don't smoke.
  • Squamous cell carcinoma of the lungs used to be the most common type of lung cancer, but its incidence has dropped (perhaps due to more cigarettes having filters). These cancers tend to occur in or near the large airways—the first place exposed to smoke from a cigarette. Lung adenocarcinomas, in contrast, are usually found deeper in the lungs, where smoke from a filtered cigarette would settle.
  • Large cell lung cancer tends to grow in the outer regions of the lungs. These cancers are usually rapidly growing tumors that spread quickly.

Small cell lung cancer accounts for 15% of cases. It tends to be aggressive and may not be found until it has already spread (especially to the brain). While it usually responds fairly well to chemotherapy, it has a poor prognosis.

Other, less common types of lung cancer include carcinoid tumors and neuroendocrine tumors.

Careful staging—figuring out the extent of a lung cancer—is important in designing a treatment regimen. Non-small cell lung cancer is broken down into five stages: stage 0 to stage IV. Small cell lung cancer is broken down into only two stages: limited stage and extensive stage.

Determining Metastasis

Lung cancer most commonly spreads to the liver, the adrenal glands, the brain, and the bones. Common tests to determine if this has occurred include:

  • CT scan of the abdomen to check for spread to the liver or adrenal glands
  • MRI of the brain to look for metastases to the brain
  • Bone scan to test for metastases to bones, especially the back, hips, and ribs
  • PET scan to look for metastases essentially anywhere in the body: This can sometimes replace other tests for metastasis listed above.

Differential Diagnoses

You may be feeling overwhelmed by what your symptoms could mean and any abnormality your doctor has seen (or may see) on an X-ray or CT scan. While lung cancer is a possibility, your doctor will consider a variety of conditions when working to make a diagnosis.

Physical symptoms that occur in cases of lung cancer could also occur with:

Likewise, the finding of a mass or nodule on imaging could instead be due to these other conditions:

  • Pneumonia
  • Fungal or parasitic infections
  • Empyema or abscess
  • Benign lung tumor (e.g., pulmonary hamartoma)
  • Granuloma
  • Granulomatous infections
  • Round atelectasis (partial lung collapse, often as a result of prior surgery)
  • Bronchogenic cysts
  • Lymphoma
  • Metastatic cancer (spread from a primary tumor in another part of the body)

Findings of indeterminate pulmonary nodules on CT scan are very common, but the majority of them prove not to be lung cancer.

A Word From Verywell

Knowing what's behind a screening or diagnostic test that turns up a spot, shadow, or nodule can be daunting—for some, to the point that they don't seek further testing. While it's true that it could be lung cancer, it's also possible that it may not be. Whatever the cause, early diagnosis is always best. If it does end up being lung cancer, know that the sooner it is caught and treated, the better your chance for survival.

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Article Sources

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