Lung Nodule

Western Toronto Thoracic Associates

What is a Lung Nodule?

A lung nodule is something seen on medical imaging of the chest such as in an x-ray. Lung nodules are generally round, less than 3 cm, and stand out from surrounding normal lung tissue. Any finding that is larger than 3 cm is referred to as a lung mass. Lung nodules can represent different findings including a variety of benign conditions (non-cancer) or malignant conditions (cancer). It is important that lung nodules be assessed because the risk of being malignant varies between individuals and identifying cancer early provides a better chance for cure.

How are Lung Nodules Found?

The two most common medical images that identify lung nodules are the chest x-ray and computed tomography (CT) scan.

  • Chest Xray – An image is created by passing x-rays through the chest with different tissues absorbing the x-rays differently which creates a picture.
  • CT Scan - Elliptical x-rays are used to construct a two dimensional image of the chest that can be viewed from different angles. CT scans are more accurate than chest x-rays and can identify smaller nodules as well as more details regarding nodule shape and appearance.

Most nodules are “incidental findings” which means the patient does not have symptoms and the medical image was taken for a different unrelated reason. Other nodules are considered “symptomatic” which means the patient had symptoms that may be related to the nodule. Symptoms that may cause a physician to look for a lung nodule include:

  • Infection with respiratory symptoms (fever, cough, increased phlegm, etc.)
  • Blood in a patients phlegm
  • Chronic cough
  • Severe weight loss
  • Profuse night sweats and/or intermittent fevers
  • Others

What Causes a Lung Nodule?

The cause of lung nodules can be categorized as being non-cancerous (benign), or as a cancerous tissue. Table 1 below provides a summary of the causes of lung nodules.

Table 1: Causes of lung nodules

Benign (non-cancerous)Malignant Growth (Cancer)
Active infections with granuloma
(a clump of inflamed tissue)
Lung Cancer of various types
Healed granulomas from past infections Metastatic cancer from elsewhere in the body that has travelled to the lung
Hamartoma (a benign tumor) Inflammatory disorders
(rheumatoid arthritis, sarcoidosis, and others)

What is the Risk of a Nodule Being Cancer?

The overall risk that a lung nodule is cancer varies greatly between individuals. Risk levels depend on two factors: characteristic appearance on imaging and patient specific risk factors for lung cancer. Table 2 lists factors on imaging and on patient history that impact the likelihood that a lung nodule could be cancer.

Table 2: Factors that impact the risk of lung cancer as the source of a lung nodule

Patient Risk Factors that Increase the Likelihood of CancerMedical Imaging Characteristics Influencing Risk of Cancer
The presence of symptoms
(cough, blood in phlegm, etc.)
Size of the nodule
Increasing age Shape of the nodule
Current of past history of smoking Rate of growth
Personal history of cancer Presence or absence of calcifications
Family history of lung cancer Cavitation (increases likelihood benign)
Past occupational exposures
(eg. to asbestos)

By combining the patient’s history and medical imaging information a physician can estimate the risk that a lung nodule represents cancer. However, a diagnosis of cancer requires a tissue sample – either from a biopsy or from surgery.

What Further Investigations Should I Expect?

The first step in evaluating a lung nodule is to compare the current image to older medical images. This determines if the lung nodule is a new finding and/or how fast the nodule is growing. It is important to bring any previous chest x-rays or CT scans you may have on CD to your appointment. Nodules that are stable over a two year period are usually benign and no further workup may be required.

If a lung nodule was originally identified on a chest x-ray, it is common to have a high resolution chest CT scan to further assess the nodule. Based on this CT scan, previous images, and your risk factors for lung cancer, further diagnostic tests may be appropriate. The most common tests are described below.

  • Serial CT Scans – in patients at low risk for lung cancer a lung nodule can be followed with CT scans at regular intervals to monitor for growth/change.
  • Positron Emission Tomography (PET) Scan – In this study the patient is injected with sugar molecules with a tracer attached to them. Lung nodules that are growing or multiplying rapidly take up the sugar the most and appear bright on imaging. Brighter nodules are more suggestive of cancer.
  • Transthoracic Lung Biopsy – A needle is guided into the patient’s chest to sample the lung nodule so that a pathologist can determine if it contains cancer cells.
  • Bronchoscopic Lung Biopsy – A fiberoptic camera is guided through the airways of the lung and node biopsy’s can be taken from inside. Ultrasound images from inside the lung can also be used.
  • Surgical Removal of the Nodule –Surgical removal is an option for patients with findings and history highly suspicious for lung cancer. In this case, the diagnosis of lung cancer is made after the surgery when the removed tissue is evaluated. A variety of surgical procedures are possible.

It is important to discuss the risks and benefits of different diagnostic and therapeutic interventions with your physician. Each patient has their own preferences which are taken into account when deciding on the most appropriate diagnostic evaluation of a lung nodule. You should come to your appointment ready to discuss any questions you have regarding these procedures.


  1. Gould M et al. Evaluation of patients with pulmonary nodules: when is it lung cancer?
    CHEST 2007;132:108-130.
  2. Evidence for the treatment of patients with pulmonary nodules: when is it cancer?
    CHEST 2007;132:96-107.