What Does Having a Nodule on the Lung Mean?

If you have been told you have a lung nodule or lung nodules on an x-ray, you're probably very frightened. Lung nodules are described as "spots" that are 3 centimeters (1.5 inches) in diameter or less (lesions larger than 3 cm are referred to a lung masses. Lung nodules are very common, especially in people who have smoked, but not all lung nodules mean lung cancer; there are many possible causes.

lung nodule causes
 Illustration by Emily Roberts, Verywell

Factors such as a history of smoking, what the nodule looks like (for example, if calcifications are present), and more can help your doctor estimate the chance that the nodule is malignant or benign. Diagnosis usually includes a CT scan or other studies, but a biopsy is needed to make a conclusive diagnosis. Treatments will vary depending on the specific cause of the nodule.

It's important to state right away that the majority—at least 60 percent of lung nodules overall—are not cancerous. We will talk about these possible causes, but it's equally important to note that if a nodule is lung cancer there is still a good chance that it can be cured. A nodule, by definition, is less than three centimeters in diameter, and at this size, many lung cancers are very curable. Yet even for lung cancers that are larger, the treatment and survival rates for lung cancer have improved significantly in just the past few years.

A final point before beginning is to note that following through on getting a diagnosis is important even if you've never smoked. At the current time, there are more former smokers and never smokers who develop lung cancer, than people who smoke. Anyone who has lungs can get lung cancer, and in fact, lung cancer has been significantly increasing among one group: young, never-smoking women.

Definition of Lung Nodules

A lung nodule is defined as a “spot” on the lung that is 3 centimeters (about 1.5 inches) in diameter or less. These nodules are often referred to as "coin lesions" when described on an imaging test. If an abnormality is seen on an x-ray of the lungs is larger than 3 centimeters, it is considered a “lung mass” instead of a nodule and is more likely to be cancerous.

Lung nodules usually need to be at least one centimeter in size before they can be seen on a chest x-ray, whereas nodules as small as one to two millimeters may sometimes be seen on a CT scan. 

Prevalence

Lung nodules are quite common and are found on one in 500 chest x-rays, and one in 100 CT scans of the chest. Approximately 150,000 lung nodules are detected in people in the United States each year. Roughly half of people over the age of 50 who smoke will have nodules on a CT scan of their chest.

If a potential nodule is seen on a chest x-ray, it is important to have a CT scan. Small cancers can be missed on a chest x-ray.

Symptoms

Most lung nodules do not cause any symptoms and are found “accidentally” or "incidentally" when a chest x-ray is done for some other reason. If symptoms are present, they may include a cough, coughing up blood, wheezing, shortness of breath (often vague at first and only with activity), or respiratory infections if the nodule(s) is located near a major airway. 

Causes

Lung nodules can be either benign (non-cancerous) or malignant (cancer). The most common causes overall include granulomas (clumps of inflamed tissue due to an infection or inflammation) and hamartomas (benign lung tumors). The most common cause of malignant lung nodules includes lung cancer or cancers from other regions of the body that have spread to the lungs (metastatic cancer).

Nodules can be broken down into a few major categories.

  • Infections: Infectious causes of nodules may include bacterial infections such as tuberculosis and other mycobacterial infections, fungal infections such as histoplasmosis, blastomycosis, aspergillosis, and coccidiomycosis, and parasitic infections such as ascariasis (roundworms), echinococcus (hydatid cysts), and paragonimous (liver flukes). When the immune system "walls off" areas of infection it often forms granulomas.
  • Inflammation: Conditions such as rheumatoid arthritis, sarcoidosis, and Wegener's granulomatosis, as well as pneumoconioses such as silicosis can also lead to granulomas. 
  • Benign tumors: Benign lung tumors such as hamartomas (the most common benign lung tumor), bronchial adenomas, fibromas, blastomas, neurofibromas, and hemangiomas. can show up as a nodule in the lungs on x-ray.
  • Malignant tumors: Cancers that may appear as a nodule includes lung cancer, lymphomas, sarcomas, and carcinoid tumors (neuroendocrine tumors). 
  • Metastases: Lung nodules may also be due to metastases from other cancers such as breast cancer, colon cancer, bladder cancer, and prostate cancer. When a nodule is due to a metastasis from another cancer, there are often multiple lung nodules present.
  • Other benign nodules: Pulmonary infarctions (areas of lung tissue that have lost their blood supply), blood vessel abnormalities (AV malformations), atelectasis (collapse of part of a lung), pulmonary fibrosis, and amyloidosis are all other possible causes of a lung nodule.

Diagnosis

The first thing your doctor will want to do if she sees a lung nodule on your x-ray is to obtain any previous x-rays you have had and compare them. If the nodule or nodules have been present for a long time, further tests may not be needed. If the nodule is new or you don’t have any prior x-rays to compare, further workup may be needed.

If a nodule is found on a chest x-ray, the first step will usually be to do a CT scan of your chest. Other tests such as an MRI or bronchoscopy may be needed.

At this point, your doctor will want to know your history as well as any risk factors you have for any type of lung nodules (see below). For example, if you have recently traveled, a fungal infection may be more likely, whereas if you have smoked, a malignant tumor may be more likely. Characteristics of the tumor as seen on your CT scan will also be evaluated.

A PET scan is sometimes helpful in further defining a nodule. Unlike CT scans and MRI which are "structural" tests, a PET scan is a "functional test." A CT or MRI scan cab find lesions in the lungs but doesn't really give a measure of what is happening in a nodule. With a PET scan, a small amount of radioactive sugar is injected into your blood stream. Actively growing tumors take up more of the sugar which lights up on the exam. This can be helpful in distinguishing a growing tumor from a scar tissue as a growing tumor will take up more of the sugar. This is especially helpful for those who have had previous chest radiation, lung infections, or surgery which may result in scar tissue. 

If a nodule does not appear to be growing or has characteristics of a benign tumor, (has "low probability" of being cancer) a "wait and watch" approach may sometimes be taken, with a CT scan repeated after a certain period of time. Single solitary nodules that have remained unchanged for a period of two or more years do not generally need any further workup.

Biopsy of Pulmonary Nodules

Unfortunately, a lung biopsy is often needed to know for sure what is causing a nodule. Thankfully, newer and less invasive methods of sampling tissue are now often available. This may be important even if your doctor is fairly sure what is causing the nodule or nodules.

An example is when nodules are thought to be metastatic cancer from another tumor such as breast cancer. Recent research suggests that even when a lung nodule is found in a person who might be expected to have lung metastases, only half of the nodules were metastases when biopsied. Up to 25 percent, rather, were a second primary lung cancer. 

Depending on the location of the nodule, a fine needle biopsy may be done. Sometimes an endobronchial ultrasound and biopsy can be done as part of a bronchoscopy. At times an open biopsy may be needed. Even when this is the case, newer techniques, such as video-assisted thoracoscopic surgery (VATS) can often be done instead of a thoracotomy.

Benign vs. Malignant Nodules

Overall, the likelihood that a lung nodule is cancer is 40 percent, but the risk of a lung nodule being cancerous varies considerably depending on several factors.

In people less than 35 years of age, the chance that a lung nodule is cancer is less than 1 percent, whereas half of lung nodules in people over age 50 are malignant (cancerous).

Other factors that raise or lower the risk that a lung nodule is cancer include:

  • Size: Larger nodules are more likely to be cancerous than smaller ones. 
  • Smoking: Current and former smokers are more likely to have cancerous lung nodules than never smokers. Learn the percentage of smokers who get lung cancer.
  • Occupation: Some occupational exposures raise the likelihood that a nodule is cancer.
  • Medical history: Having a history of cancer increases the chance that a nodule could be malignant. 
  • Family history: Those who have nodules and a family history of lung cancer are more likely to have cancerous nodules than those without a family history.
  • Symptoms: The chance that a nodule is lung cancer is greater if other signs or symptoms of lung cancer are present.
  • Shape/appearance of the nodule: Smooth, round nodules are more likely to be benign, whereas “spiculated” nodules, or those with irregular or lobular borders are more likely to be cancerous.
  • Solid/non-solid: Nodules that are part solid rather than solid are more likely to be cancerous
  • Growth: Cancerous lung nodules tend to grow fairly rapidly with an average doubling time of about four months, while benign nodules tend to remain the same size over time.
  • Calcification: Lung nodules that are calcified are more likely to be benign.
  • Cavitation: Nodules described as “cavitary,” meaning that the interior part of the nodule appears darker on x-rays, are more likely to be benign.
  • Ground glass nodules: Nodules that are described as having a ground glass appearance are often a challenge and can be either benign or malignant. Due to this difficulty, a biopsy of these lesions is usually needed.
  • The number of nodules: Those who have multiple lung nodules are more likely to have cancer than those who have a solitary or only a few pulmonary nodules. The most common cause of multiple lung nodules is metastatic cancer from the breast, prostate, colon, or bladder (though many tumors can metastasize to the lungs).
  • Location of the nodules: Lobules located in the right or left lower lobes or the right middle lobe of the lung are less likely to be cancerous than those located in the left or right upper lobes.
  • Ethnicity and geographic location: If you have traveled outside the United States, a lung nodule is more likely to be benign. For example, recent studies have found that lung nodules due to schistosomiasis, a parasitic infection, are fairly common in African imigrants. Likewise, nodules related to fungal infections, such as coccidiomycosis are common in the Southwest.

    Indeterminate Lung Nodules

    The number of lung nodules that are read by radiologists as "indeterminate" has increased with the advent of lung cancer screening. Hearing that your nodule or nodules are indeterminate can be confusing. Isn't it obvious? Unfortunately, there are times when it is impossible on imaging tests alone to know whether a nodule is malignant—even after considering all of the factors above. In order to answer this question, a biopsy must be done. Thankfully, radiologists, surgeons, and pathologists together are finding less invasive methods of sampling tissue. .

    Lung Cancer Screening

    Lung cancer screening in appropriate people has been found to decrease the mortality rate from lung cancer by 20 percent. But as with any screening test, there is the risk of false positives, and it's common to find nodules on CT screening. But finding nodules does not always mean cancer. In fact, studies thus far estimate that only around five percent of nodules found on a first lung CT screening are cancerous.

    Treatment

    The treatment of lung nodules varies widely depending upon the cause, whether they are related to infections, inflammation, cancer, or other conditions. Most benign lung nodules, especially those that are present and haven’t changed over a period of a few years, can be left alone.

    A Word From Verywell

    If you've heard that you or a loved one have a lung nodule you are probably feeling a combination of nervous and overwhelmed. There are so many different possibilities and some of these are frightening. It may help a little to consider that the majority of nodules are not cancer, and even those that are may be curable with surgery.

    If you decide to research your nodule online it's important to note that the science is changing rapidly. Newer diagnostic techniques are becoming available as well as new treatments each year. Since medicine is changing so rapidly, It's important to be your own advocate in your medical care. Many people have found their lung cancers early by being persistent in getting answers for their questions. If you aren't getting answers, ask more questions. Consider getting a second opinion regardless of what you hear. When choosing a site for a second opinion, many physicians recommend getting an opinion at one of the larger National Cancer Institute-designated cancer centers. Not only may these centers be on top of the latest treatments, but a consultation with a specialist in lung nodules may end up saving you unnecessary biopsies and surgery if the risk that your nodule is cancer is low.

    Finally, reach out to family and friends. If your nodule turns out to be lung cancer there is an active lung cancer community that will welcome you in.

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