Your pathology report for non-small cell lung cancer (NSCLC)

by Jason Wasserman MD PhD FRCPC
June 21, 2025

Non-small cell lung cancer (NSCLC) is a category of lung cancer that includes several different types of cancer that start in the lungs. It is called “non-small cell” because the cancer cells are larger and look more mature under the microscope compared to those in another category called small cell lung cancer.

The non-small cell lung cancer category includes adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. These types are grouped together because they grow and spread in similar ways and are often treated using similar strategies.

What are the symptoms of non-small cell lung cancer?

Some people with non-small cell lung cancer do not have symptoms in the early stages. When symptoms do appear, they may include:

  • A persistent cough that does not go away.

  • Shortness of breath.

  • Chest pain.

  • Coughing up blood.

  • Fatigue or unexplained weight loss.

These symptoms can also be caused by other conditions, so additional tests are typically required to confirm a diagnosis.

What causes non-small cell lung cancer?

Non-small cell lung cancer is caused by mutations (changes) in the DNA of cells in the lung. These changes cause the cells to grow and divide uncontrollably, leading to the formation of a tumour. The most common cause of these DNA changes is cigarette smoking. However, non-small cell lung cancer can also occur in people who have never smoked. Other risk factors include exposure to secondhand smoke, air pollution, radon gas, and certain workplace chemicals.

What types of cancer are in the non-small cell lung cancer category?

The three main types of cancer in the non-small cell lung cancer category are:

  • Adenocarcinoma: This is the most common type, especially in people who do not smoke. It develops from gland-forming cells and is typically located in the outer regions of the lungs. There are two types of adenocarcinoma: non-mucinous and mucinous. Non-mucinous adenocarcinoma is more common and forms glands or small spaces filled with fluid. Mucinous adenocarcinoma is made up of cells that produce a large amount of mucin (a substance similar to mucus).

  • Squamous cell carcinoma: Squamous cell carcinoma originates from the flat cells that line the inner walls of the airways. It is strongly linked to cigarette smoking and often develops in the central part of the lungs. Squamous cell carcinoma is divided into keratinizing and nonkeratinizing types. The keratinizing type produces keratin, a substance normally found in skin, while the nonkeratinizing type does not.

  • Large cell carcinoma is a less common type of cancer. It includes tumours made of large cells that do not clearly look like either squamous cells or gland-forming cells.

Your pathology report will usually specify which type of cancer within the non-small cell lung cancer category was found.

What is the difference between non-small cell lung cancer and small cell lung cancer?

Non-small cell lung cancer and small cell lung cancer are the two main categories of lung cancer. They differ in their appearance under the microscope, growth rate, and spread, as well as in their treatment.

  • Small cell lung cancer is less common but tends to grow and spread much faster. It is strongly linked to smoking and often starts in the central parts of the lungs. Because it spreads quickly, it is usually treated with chemotherapy and radiation rather than surgery.

  • Non-small cell lung cancer grows more slowly and is more likely to be treated with surgery, especially if found at an early stage. Depending on the specific type and stage, treatment may also include chemotherapy, radiation, targeted therapy, or immunotherapy.

How is this diagnosis made?

The diagnosis of non-small cell lung cancer is usually made after a biopsy, where a small sample of tissue is removed from the lung. A pathologist examines the sample under a microscope to look at the size, shape, and arrangement of the cells. Additional tests, such as immunohistochemistry or molecular testing, may be performed to confirm the diagnosis and to identify specific features that guide treatment.

What does stage mean for non-small cell lung cancer?

The stage describes how far the cancer has spread in the body. Staging helps doctors decide the best treatment options. The stage is based on:

  • The size of the tumour.

  • Whether the cancer has spread to nearby lymph nodes.

  • Whether the cancer has spread to other parts of the body.

Staging ranges from stage 0 (very early) to stage 4 (advanced and widely spread). Staging may require imaging tests such as CT scans or PET scans and sampling of lymph nodes.

What is the prognosis for non-small cell lung cancer?

Prognosis refers to the expected outcome or chance of recovery. It depends on several factors, including:

  • The specific type of cancer within the non-small cell lung cancer category.

  • The stage at the time of diagnosis.

  • Whether the cancer can be removed completely with surgery.

  • Whether the tumour has specific molecular changes (such as EGFR, ALK, or KRAS mutations).

  • Your age, overall health, and other medical conditions.

Generally, cancers that are found early and can be removed with surgery have a better prognosis. Advanced cancers that have spread are harder to treat, but new treatments like targeted therapy and immunotherapy have improved outcomes for many people.

Questions to ask your doctor

  • What type of cancer do I have within the non-small cell lung cancer category?

  • What is the stage of my cancer?

  • What are my treatment options?

  • Are there any molecular or genetic features in my tumour that affect treatment?

  • What can I expect in terms of prognosis and next steps?

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