Diagnosing non-small cell lung cancer

Several types of tests are used to diagnose non‑small cell lung cancer (NSCLC). These include imaging, biopsies, and laboratory tests. The results help confirm the diagnosis and guide treatment decisions.

Physical examination

A doctor will perform a physical examination by examining the patient and listening to their chest. Lung function – how well the lungs are working – may also be assessed using a device called a spirometer.

Imaging

Imaging tests are painless, non-invasive procedures used to capture pictures of the inside of the body. A radiologist looks at these images and checks for any abnormalities. Examples used in the diagnosis of non-small cell lung cancer include:

An X-ray, which uses low-dose radiation to take a picture of the inside of the body.
A computed tomography (CT or CAT) scan, which uses X-ray techniques to create detailed 3D pictures of the inside of the body.
A positron emission tomography (PET) scan, which uses a small amount of a radioactive substance to show how active cells are in the body.

Biopsy

A biopsy involves taking a sample of tissue from a suspected tumor, which is then sent for laboratory tests. It can be done in several ways:

A needle biopsy, where a very fine needle is carefully guided into the lung to remove a small sample of tissue or fluid. This is usually done using imaging, such as CT or ultrasound, to help the doctor place the needle accurately. A local anesthetic is used to numb the area.
A bronchoscopy, which uses a thin tube with a light and lens (a bronchoscope) to look inside the airways. Tissue samples can also be taken during the procedure.
A thoracoscopy or mediastinoscopy are surgical procedures that allow doctors to look inside the chest and take tissue samples.
An endobronchial ultrasound (EBUS) biopsy, which uses a thin bronchoscope with an ultrasound probe to view the airways and nearby lymph nodes and take tissue samples.

Laboratory tests

Tissue or blood samples can be examined using several techniques, including:

Microscopy, where the cells are examined under a microscope to look for any abnormal changes.
Immunohistochemistry (IHC), which uses antibodies for particular markers of cancer, such as PD-L1 (programmed death-ligand 1) or MET. The antibodies are joined to a fluorescent dye, so they can be seen under a microscope and help doctors confirm whether there are cancer cells there and what type they are.
Blood tests, which may be done to check general health and look for certain substances (biomarkers) that can sometimes be present in patients with non-small cell lung cancer.
DNA or RNA testing, such as next-generation sequencing (NGS), to look for changes in specific genes (mutations) in cancer cells. This information is helpful because some drugs are designed to target these changes, so these tests can help guide treatment decisions.

Examples of genes which might be checked for mutations are:

ALK (anaplastic lymphoma kinase) gene.
BRAF gene.
EGFR (epidermal growth factor) gene.
HER2/ERBB2 (human epidermal growth factor receptor 2/Erb-B2 receptor tyrosine kinase 2).
KRAS gene.
MET (mesenchymal-epithelial transition) gene.
NTRK (neurotrophic tyrosine receptor kinase) gene.
RET gene.
ROS1 gene.

Further tests

After non-small cell lung cancer is diagnosed, further imaging may be performed to see whether the cancer has spread. These tests help doctors understand the stage of the cancer and plan the most appropriate treatment. They can include:

Magnetic resonance imaging (MRI), which uses magnets and radio waves to make detailed pictures of areas inside the body.
A bone scan, to see if the cancer has spread to the bones. A small amount of radioactive material is injected into the blood, and a camera then scans the body and detects if the material has collected anywhere.

References

Macmillan Cancer Support. X-ray. https://www.macmillan.org.uk/cancer-information-and-support/diagnostic-tests/x-ray. Updated Jan 24, 2022. Accessed Mar 4, 2026.
Macmillan Cancer Support. CT scan. https://www.macmillan.org.uk/cancer-information-and-support/diagnostic-tests/ct-scan. Updated Jan 24, 2022. Accessed Mar 4, 2026.
Cancer Research UK. Tests for lung cancer. https://www.cancerresearchuk.org/about-cancer/lung-cancer/getting-diagnosed/tests-for-lung-cancer. Updated Oct 8, 2025. Accessed Mar 4, 2026.
National Cancer Institute. Non-small cell lung cancer treatment (PDQ®)–patient version. https://www.cancer.gov/types/lung/patient/non-small-cell-lung-treatment-pdq. Updated May 16, 2025. Accessed Mar 4, 2026.