Lung cancer screening and diagnosis comprises two steps:

  1. Screening high-risk individuals who do not have any signs or symptoms of lung cancer
  2. Diagnostic tests to confirm the presence or absence of lung cancer. Once these tests confirm the presence of lung cancer, they also tell the doctor the type of lung cancer and its stage, which helps the oncologist frame the best possible treatment plan for that particular case.

Diagnostic tests are done after screening has detected the presence of cancer in the lungs or the doctor strongly feels the need to rule it out after he has taken the medical history and physical examination, which indicate the presence of lung cancer risks, symptoms, and signs in the individual.

Some lung cancers are detected by screening, but most lung cancers are found because diagnostic tests are performed due to the presence of symptoms.

Therefore, lung cancer screening and diagnosis become most vital when dealing with a suspected case of lung cancer. It enables prompt treatment, which ultimately gives a better prognosis.

What is lung cancer screening and how is it done?

Screening for lung cancer is testing for cancer when there are no presenting symptoms or history. This can help find cancer early. Early detection in the initial stages of cancer leads to prompt treatment and a better prognosis.

The onset of symptoms signifies that cancer may have begun to spread and is advanced, in which case it becomes difficult to treat.

Being advised a screening does not necessarily mean you have cancer – it is meant to confirm that you do not have cancer or you have it.

If the screening tests detect an abnormality, the patient is subjected to diagnostic tests for a more detailed analysis of the disease.

The recommended screening tests for lung cancer include:

  • Low-dose computed tomography (low-dose CT scan, LDCT): LDCT uses low-dose radiation to take a series of very detailed pictures of areas of your lungs with an X-ray machine.
  • Chest x-ray:
  • Sputum cytology: Sputum cytology is a procedure in which sputum expectorated from the lungs is examined under a microscope to detect cancer cells.

Who should be screened for lung cancer?

The U.S. Preventive Services Task Force (USPSTF) recommends annual lung cancer screening for people who:

  • Are between 50 and 80 years old
  • Have a smoking history of 20 pack-year or more, and
  • Still smoke now or have quit within the past 15 years

A pack-year is defined as smoking an average of one packet (20 cigarette pack) of cigarettes per day for one year. For example, a person with a 20-pack-year history has smoked one pack of twenty cigarettes a day for 20 years or two packs a day for 10 years.

When should screening not be done?

The Task Force recommends that annual screening for lung cancer stop when the person being screened

  • Turns 81 years old, or
  • Has not smoked in 15 or more years, or
  • Develops a health problem that makes him or her unfit to undergo lung cancer surgery after lung cancer has been detected.

Diagnosis guidelines for lung cancer

If you have symptoms of lung cancer, such as dyspnea (breathlessness) on exertion or at rest, and/or a persistent cough, you must see your pulmonologist (lung specialist) who will send you through the diagnostic drill to confirm the presence of lung cancer.

This diagnostic drill will consist of blood tests, sputum cytology, imaging studies, and biopsy procedures

Blood tests

Blood tests help to get a knowhow of a person’s overall health and whether he is fit for surgery if required.

1. A complete blood count (CBC). This blood test looks at your overall blood picture. For example,

Whether his blood cell counts are within normal limits

  • A low hemoglobin count will tell whether he is anemic.
  • A low platelet count will tell that he may be having bleeding disorders
  • Below normal low white blood cell count will indicate that he is at risk of infections.

CBC could be repeated periodically during treatment, as many cancer drugs can affect blood cell count.

2. Blood chemistry tests.

  • Liver function and kidney function tests are done to find abnormalities in your organs, such as the liver or kidneys.
  • If cancer has spread to the bones, it might cause increased blood levels of calcium and alkaline phosphatase.
  • Arterial blood gas test measures the amount of oxygen and carbon dioxide in the arterial blood to see if the exchange of gases is taking place properly in the lungs.

If the lung parenchyma is significantly damaged, the oxygen level in the arterial blood will be less and the carbon dioxide level will be high.

Lung function tests

Pulmonary (Lung) function tests (PFTs) are often done after lung cancer is diagnosed to see how well or how badly the function of your lungs is affected.

This becomes especially important if surgery is indicated for treatment. Surgery for lung cancer involves removing part or all of a lung, so it’s important to know the functioning status of your lungs.

Surgery, if indicated for lung cancer treatment, may not be an option if the lungs are damaged due to other factors such as smoking or COPD.

Sputum cytology

A sample of sputum coughed up from the lungs is tested in the lab for the presence of cancer cells. It is performed on the early morning sample for three days in a row.

This test is helpful to detect cancer that originates in the major airways of the lungs, such as squamous cell lung cancers.

 Chest X-ray

Your doctor orders a chest x-ray first because it can be done quickly and results are seen immediately. A tumor in the lung is seen as an opaque white mass, but so does a pneumonic patch or a lung abscess. A chest x-ray, therefore cannot give a definite diagnosis.

However, any patch seen in the lungs is an indication for further detailed studies.

These further studies will tell the doctor whether you have lung cancer, what type it is, and whether it has spread.

CT scan

Your doctor will suggest a CT scan after the lung x-ray. A CT scan creates detailed images of the lungs, which can be viewed on the computer.

Your doctor may order a contrast CT scan, which improves the quality of the images. In this type of CT scan, you will be injected intravenously with a special dye called contrast medium.

Before having a CT scan, you’ll be given an injection containing a special dye called a contrast medium, which helps to improve the quality of the images by highlighting certain features.

A contrast CT scan remains the standard imaging test for the initial assessment of patients with suspected lung cancer. A CT scan is painless and takes 10 to 30 minutes.

It will tell you that there is a lesion/tumor, but it cannot definitely say that the lesion is malignant or benign. Only a biopsy or PET-CT scan can confirm that.

PET-CT scan

Your doctor will order a PET-CT scan if the results of a CT scan show you have a tumor.

The PET-CT scan (positron emission tomography-computerized tomography) can show if there are active cancer cells. This can help to diagnose and choose the best treatment.

Before doing a PET-CT scan, you’ll be injected with a slightly radioactive material. In this imaging procedure, you will lie down on a table, which slides into the PET scanner. The scan is painless and takes 30 to 60 minutes.

Bronchoscopy and biopsy

If a CT scan shows there might be cancer in the central part of your lungs, your doctor will order a bronchoscopy.

During a bronchoscopy, the pulmonologist inserts a thin tube with a camera at the end, called a bronchoscope, through your mouth or nose, down your throat, and into your bronchi (airways).

The procedure is uncomfortable, so you’ll be given a sedative before it starts and a local anesthetic to numb your throat. The procedure takes around 30 to 40 minutes.

It allows a doctor to see the inside of your airways and remove a small sample of tissue (biopsy) from the suspected tumor.

There is a newer procedure is called an endobronchial ultrasound scan (EBUS), which combines a bronchoscopy with an ultrasound scan.

The advantage of this new procedure is that the ultrasound probe on the end of the camera also allows the doctor to also locate the mediastinal lymph nodes in the center of the chest so he can take a biopsy from the nodes. A biopsy from a lymph node can show if cancerous cells have spread to the lymph nodes.

The procedure takes around 90 minutes.


A thoracoscopy is usually done under general anesthesia. It allows a doctor to examine the suspected area of your lungs and take samples of tissue and fluid, which are then sent to a laboratory for testing.

This is done through two or three small cuts made in your chest wall to pass a bronchoscope-like tube into your chest.

You may need to stay in the hospital overnight and any fluid formed in your lungs will be drained.

Mediastinoscopy with biopsy

A mediastinoscopy with biopsy allows a doctor to examine the mediastinum. It is the area at the center of your chest between your lungs and take a biopsy sample.

For this test, you’ll be given general anesthesia and you may require to stay in the hospital for a couple of days.

In this procedure, the doctor makes a small cut at the bottom of your neck. He, then, passes a thin tube with a camera at the end into your chest.

With the mediastinoscope, the doctor is able to take biopsy samples of the mediastinal lymph nodes for testing in the lab. These lymph nodes are usually the first place that lung cancer spreads to.

Percutaneous needle biopsy

During a percutaneous needle biopsy, a local anesthetic is used to numb the skin where the doctor is going to insert the needle to take the biopsy.

Under a CT scan or ultrasound guidance, the doctor inserts the biopsy needle through your skin into your lung to the site of a suspected tumor.

With the help of the needle, the doctor removes a small amount of tissue from the suspected tumor and sends it to the lab for testing.

Early lung cancer screening and diagnosis are crucial in the prognosis of the disease. Screening can help in early detection and diagnostic tests help in confirming the presence so that the right treatment options can be exercised.