What is non-small cell lung cancer?

Non-small cell lung cancer (NSCLC) is a group of lung cancers that behave in similar ways. These cancers start in the cells that line the airways and lung tissue.

Around 80–85% of lung cancers are non-small cell lung cancer. These cancers are called “non-small cell” to distinguish them from small cell lung cancer.

Types of non-small cell lung cancer

There are three main types of non-small cell lung cancer:

Adenocarcinoma, which starts in cells in the airways that produce mucus.
Squamous cell carcinoma, which starts in flat cells that cover the surface of the airways.
Large cell carcinoma, which is a less common type named after how the cells look under a microscope.

There are also other, less common, types of non-small cell lung cancer, such as adenosquamous carcinoma and sarcomatoid carcinoma. Different forms of non-small cell lung cancer have particular types of cancer cells, which grow and spread in different ways. All types of non-small cell lung cancer can start in any part of the airways and can spread to other parts of the body.

What causes non-small cell lung cancer?

Smoking, or exposure to tobacco smoke, is the most common cause of non-small cell lung cancer. Other factors, such as age, exposure to chemicals called carcinogens (e.g. asbestos), a family history of lung cancer, or exposure to radiation, can also contribute. People who have never smoked can still develop non-small cell lung cancer, which may be related to air pollution.

Doctors do not need to know why someone has developed non-small cell lung cancer to decide on the most appropriate treatment.

References

National Comprehensive Cancer Network® (NCCN®). NCCN guidelines for patients®. Early and locally advanced non-small cell lung cancer. 2026. https://www.nccn.org/patients/guidelines/content/PDF/lung-early-stage-patient.pdf. 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.
Cancer Research UK. Types of lung cancer. https://www.cancerresearchuk.org/about-cancer/lung-cancer/stages-types/types. Updated Jan 13, 2026. Accessed Mar 4, 2026.