Doctors use chest X-rays, CT scans, and PET scans to diagnose lung cancer. Identifying the type of lung can help decide suitable treatment options.

Lung cancer can start in different parts of the lung, such as the top, middle, or outer membranes. They can also vary in terms of histology, or structure.

A range of tools can help diagnose lung cancer, including lung imaging scans. The scans can show the location and severity of the cancer and may even indicate its type.

In this article, we discuss what lung cancer can look like on an X-ray or otherwise. We also look at the various types and the differences between them.

The two main types are small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC). SCLC grows faster and is harder to treat. Within NSCLC, there are also subtypes, such as adenocarcinoma and squamous cell cancer.

The characteristics of lung cancer will depend on the type, which will in turn affect the way cancer develops and the outlook.

Below are some characteristics of various types of lung cancer.


SCLC accounts for around 15% of cancers that develop in the airways. Smoking is a major risk factor. However, exposure to asbestos, radiation, and air pollution also increases the risk.

There are two subtypes: small-cell carcinoma, or oat cell cancer, and combined small-cell carcinoma.

A person with limited stage SCLC will have cancer in or near the area where it started. If a person has extended stage SCLC, it will have spread to other parts of the body, and it will be harder to treat.

SCLC tends to grow more quickly than other types of lung cancer and can be hard to treat. Even so, around 27% of people who receive a diagnosis in the early stage will live another 5 years or more.

On a chest X-ray, these tumors may appear as white masses located toward the center of the lungs.


There are several types of NSCLC. The type will depend on where it starts in the lungs.

NSCLC refers to any cancer affecting lung cells that is not SCLC. Examples include:

  • adenocarcinoma
  • squamous cell cancer
  • large-cell carcinoma

Smoking, exposure to asbestos and other toxins, and having HIV are all possible risk factors.

NSCLC grows more slowly than SCLC. A person who receives a diagnosis in the earliest stage will have a 63% chance of living at least another 5 years.


About 40% of lung cancers are adenocarcinoma, which is a type of NSCLC. It usually starts in the outer portions of the lungs and grows slowly. There are several types of adenocarcinoma.

Adenocarcinoma starts on the outer part of the lungs and develops as round nodules in the lungs. The nodules first appear in cells that produce mucus.

Smoking is the main risk factor for adenocarcinoma. However, it is also the type of lung cancer that most frequently develops in nonsmokers.

Squamous cell carcinoma

Around 25% of all lung cancer cases are squamous cell carcinoma. This type starts in the cells that line the airways in the lungs.

The tumors usually appear near one of the lung’s main airways. As the tumors grow, they may extend into the wall of the chest.

Large-cell (undifferentiated) carcinoma

This type of carcinoma accounts for around 10% of all lung cancer cases.

It can appear anywhere in the lungs and grows rapidly. This makes it difficult to treat.


A layer of cells called the mesothelium surrounds the lungs, heart, abdomen, and other organs. The pleura, a type of mesothelium, surrounds the lungs.

Pleural mesothelioma, or simply mesothelioma, is cancer that first develops in this layer of tissue.

According to the American Cancer Society (ACS), a chest X-ray may reveal:

  • a thickening of the pleura
  • calcium deposits on the pleura
  • fluid between the lungs and the chest wall
  • other changes in the lungs that can suggest mesothelioma

Pancoast tumor

Pancoast tumors are a rare type of lung cancer. They develop near the top of the lung, and they account for 3–5% of lung cancer cases.

Pancoast tumors cause a complex of symptoms because of the nearby structure they can affect. The symptoms include numbness in the fingers or hands, excessive sweating, and Horner’s syndrome.

Metastatic cancers

When cancer spreads beyond the place where it first formed, this is metastasis.

Cancer can spread from the original location to other parts of the body through the blood. A tumor can also spread by growing into nearby tissues.

Metastatic lung cancer is cancer that has spread to another part of the body, for example, the liver. In this case, it is still lung cancer.

If a person has breast cancer that reaches a lung, it will not be lung cancer. It will be metastatic breast cancer.

A doctor will use a chest X-ray when diagnosing any type of cancer, because other cancers often spread to the lungs.

A doctor may recommend tests for lung cancer if a person has a persistent cough, chest pain, or hoarseness. They may also find signs of lung cancer during a regular checkup.

The doctor will start by asking a person about:

  • symptoms
  • their family and personal medical history
  • lifestyle factors, such as smoking

They will also carry out a physical examination.

If they believe a person may have lung cancer, they will recommend some tests.

Chest X-ray

A chest X-ray is usually the first test, but further tests will need to confirm that cancer is present.

If an X-ray shows a growth, it is not necessarily cancer.

According to the American Thoracic Society, up to 50% of adults who have a chest X-ray or a CT scan of the lungs have at least one growth. However, fewer than 5% of these growths are cancerous.

CT scan and other scans

A CT scan uses multiple X-ray images to create a detailed view of the lungs. It is more reliable than an X-ray for showing lung tumors.

It can also show the size, shape, and position of a tumor and whether cancer affects the lymph nodes and other parts of the body.

PET scans can also provide more detailed information. A doctor may recommend a PET scan alongside a CT scan for a more detailed impression.

Biopsy and lab tests

A lung biopsy is the only way to confirm that lung cancer is present.

This involves taking a small sample of lung tissue for examination under a microscope. The results can show whether cancer is there, and if so, what type.

A doctor may also suggest a sputum test. In this case, they will take a sample of phlegm to send to a lab for testing.

Lung cancer is easiest to treat in the early stages, but people often have no symptoms early on.

However, if symptoms appear, they include:

As lung cancer grows and spreads, other symptoms can also appear.

Learn more about the signs and symptoms of lung cancer here.

Treatment options depend on the type of lung cancer, stage, and factors specific to each individual.

A doctor may recommend one or more of the following:

A doctor will work with a person to develop a suitable treatment plan.

Lifestyle adjustments, such as eating a healthy diet, getting exercise, and quitting smoking, may also help prolong a person’s life and reduce the severity of symptoms.

The outlook for lung cancer depends on the:

  • stage of cancer at diagnosis
  • type of cancer
  • age and overall health of the individual

Experts calculate a person’s chances of surviving cancer at least 5 more years after a diagnosis by studying past figures.

According to the ACS, the chances of surviving 5 years or more with SCLC and NSCLC are as follows:

localized (still in the original location)63%27%
regional (has spread to nearby areas)35%16%
distant or metastatic (has spread throughout the body)7%3%

Quitting smoking and avoiding secondhand smoke can help prevent lung cancer from starting or even progressing, in some cases. A doctor can advise about effective ways to do this.

Products are also available to purchase online that can help people quit smoking.

Read this article in Spanish.