What Are Multiple Lung Nodules?

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Multiple lung nodules mean that you have two or more lesions in your lungs. Multiple lung nodules are also called pulmonary nodules. These lesions can be seen on an imaging scan like an X-ray. You may not have any symptoms of multiple lung nodules.

If you've had a chest X-ray and learned that you have multiple, lung nodules, you might worry it means you have cancer. If you only have one lung nodule (solitary pulmonary nodule), it probably is not cancer. However, if you have several or many lung nodules, the risk of cancer increases.

This article will go over what causes multiple lung nodules and how they can be diagnosed. You will also learn how multiple lung nodules are treated.

Multiple Lung Nodules: Characteristics

Multiple lung nodules look like spots or lesions on an X-ray. They usually measure 3 centimeters (roughly 1.2 inches) or less in diameter. Multiple lung nodules are a common finding, occurring in between 3.9 and 6.6 of every 1,000 chest X-rays in the United States.

Cancer is a concern when there are multiple lung nodules seen on a scan. In fact, cancer is the most common cause of multiple lung nodules. When cancer spreads from a primary tumor to other parts of the body (metastasis), nodules in the lungs can result.

That said, "most common" doesn't mean "only." There are nearly as many noncancerous (benign) causes of multiple lung nodules as there are cancerous (malignant) ones. The way that the nodules look on a scan can give providers hints about which type they are.

More Likely to Be Cancerous
  • Multiple nodules that are 8 millimeters (mm), roughly 1/4 inch, or more in diameter

  • Nodules described as "non-calcified" (with evenly distributed "ground-glass" appearance)

More Likely to Be Benign
  • Nodules that are less than 5 mm (1/5 inch) are more likely to be benign, especially when distributed in the fissures between the lobes of the lung or along the tissue that lines the lung

  • Nodules described as "calcified" (seen on X-ray with random spots and flecks)

Symptoms

Most lung nodules do not cause any symptoms. You may only find out that you have them when they're seen on a scan. When people do have symptoms of lung nodules, they can include:

Causes

Multiple lung nodules can be caused by malignant or benign diseases. Here are some of the most common causes of lung nodules.

causes of multiple lung nodules
Illustration by Jessica Olah, Verywell

Cancerous Lung Nodules

Benign Lung Nodules

  • Mediastinal lymph nodes are located along the lining of the lung. Like all lymph nodes, they can become enlarged during infection. This can sometimes be seen as a spot on an X-ray.
  • Benign tumors can also develop in the lungs. The most common are tissue malformations called hamartomas. Other types of benign tumors include fibromas, bronchial adenomas, hemangiomas, and blastomas.
  • Autoimmune disorders happen when the immune system inadvertently attacks the body's own cells. They can sometimes form granulations and growths that appear as spots on an X-ray. Causes include rheumatoid arthritis, sarcoidosis, and eosinophilic lung diseases.
  • Lung infections can sometimes appear as solitary or multiple spread-out (diffuse) nodules on a scan. Common lung infections include bacterial infections such as tuberculosis, fungal infections such as cryptococcosis, and parasitic infections such as echinococcosis.
  • Coal workers' pneumoconiosis, also known as black lung disease, occurs in around 2% of coal miners. People with the disease often have 1-millimeter to 2-millimeter lung nodules. There has been an increase in the incidence of severe black lung disease (progressive massive fibrosis) in young coal workers in Appalachia.
  • Scars from past infections can also show up on chest X-rays as nodules. Often, people never knew they were sick.

Diagnosis

The most common cause of multiple lung nodules is metastatic cancer. Providers will usually start by looking for the primary (original) tumor. Depending on what they find, a provider may order other tests—for example, mammogram or breast magnetic resonance imaging (MRI) to look for a breast tumor, or a colonoscopy to look for a colon tumor.

Other tests that might be used after finding multiple lung nodules include:

Radiologists usually prefer a combination of CT and PET scans for figuring out the cause of multiple lung nodules rather than doing each test individually.

The way the lung nodules are arranged and spread out (distributed) can also be helpful in narrowing down possible causes. For example, coal workers' pneumoconiosis most often causes nodules that are predominant in the upper lobes. In lymphoma, the nodules are usually around the airways.

If the cause of multiple lung nodules is still unclear when the imaging tests are done, a sample of tissue from your lung (lung biopsy) can be taken.

Treatment

The treatment for multiple lung nodules depends on the cause. Benign nodules can often be left alone. Nodules related to an infection can be treated with the appropriate antibiotic, antifungal, or antiparasitic drugs.

If metastatic cancer is diagnosed, treatment is based on where the tumor is. Cancer's spread is also a factor when deciding on treatment. For example:

Summary

Being told that you have multiple lung nodules can be frightening, especially if you didn't have any symptoms and are worried you could have cancer. Keep in mind that multiple lung nodules are not always cancer and may not even require treatment.

If your lung nodules are cancerous, there are usually treatments. They may not be curative, but they can reduce symptoms and help you live longer.

Frequently Asked Questions

  • What percentage of multiple lung nodules are cancerous?

    About 40% of lung nodules turn out to be cancer.

  • Can COVID-19 cause multiple lung nodules?

    Researchers studying people with COVID-19 have seen cases where people with the infection have lung nodules. Some people just have nodule while others may have several.

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