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