What Are Multiple Lung Nodules?

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If you've had a chest X-ray or other imaging and have been advised that the radiologist spotted multiple lung nodules, the first thing that may come to mind is cancer. When lung nodules occur in isolation (solitary pulmonary nodule (SPN), cancer is infrequently the case. But when there are several or many, the risk of cancer increases. Multiple pulmonary nodules (MPN) is the term used to define cases of two or more lung lesions.

Nodule Characteristics

Lung nodules will typically be seen as spots or lesions on an X-ray and measure 3 centimeters (roughly 1.2 inches) or less in diameter. They are a fairly common finding, occurring in between 3.9 and 6.6 of every 1,000 chest X-rays in the United States.

When MPN are seen on a scan, the first assumption is cancer. In fact, cancer is the most common cause of MPN and is usually the result of metastasis (when cancer spreads from a primary tumor to the other parts of the body).

But "most common" doesn't mean "only." There are nearly as many benign (noncancerous) causes of MPN as there are malignant (cancerous) ones. The way that the nodules look on a scan can suggest 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)



causes of multiple lung nodules
Illustration by Jessica Olah, Verywell

MPN may be caused by malignant or benign diseases. The more common ones can be broken up as follows.



  • Mediastinal lymph nodes are located along the lining of the lung and, like all lymph nodes, can become enlarged during infection. This can sometimes be read as a spot on an X-ray.
  • Benign tumors can also develop in the lungs, the most common of which are tissue malformations called hamartomas. Other types of benign tumors include fibromas, bronchial adenomas, hemangiomas, and blastomas.
  • Autoimmune disorders are those in which 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 a solitary or multiple diffuse nodules on a scan. These 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, still occurs in around 2% of coal miners and often manifests with 1-millimeter to 2-millimeter 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 in people who never realized they had an infection.


Since the most common cause of MPN is metastatic cancer, doctors will often begin their investigation by looking for a primary (original) tumor. Depending on what the early diagnostics say, the doctor may order a mammogram or breast magnetic resonance imaging (MRI) to look for a breast tumor, or a colonoscopy to look for a colon tumor.

Additional imaging tests can be used, including:

The current thinking among radiologists is that the combination of CT and PET scans is more useful in determining the cause of MPNs than the individual tests on their own.

If the cause of your nodules is still unclear after imaging, a lung biopsy may be performed to obtain a tissue sample.

The distribution of lung nodules can also be helpful in narrowing down causes. For example, coal workers' pneumoconiosis most often causes nodules that are predominant in the upper lobes, while lymphoma typically manifests with nodules around the airways.


The treatment of MPN will depend 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 drug.

If metastatic cancer is diagnosed, treatment would be prescribed based mainly on the location of the primary tumor and the extent of the metastases. This can vary from one cancer type to the next.

For example, nodules related to metastatic breast cancer may be treated with a combination of a lumpectomy or mastectomy, radiation therapy, chemotherapy, endocrine therapy, and newer targeted drugs like Ibrance (palbociclib).

By contrast, nodules related to the metastatic colon may be treated a colon resection accompanied by chemotherapy and targeted drugs like Avastin (bevacizumab).

Meanwhile, primary cancers like lymphoma that manifest with MPNs may require chemotherapy, radiation therapy, biologic therapy, immunotherapy, stem cell transplantation, CAR T-cell therapy, or a combination of these.

Newer techniques such as stereotactic body radiotherapy (SBRT) may be used to treat a single metastasis and, sometimes, multiple metastases. If there are few, treating the malignant nodules may improve survival.

A Word From Verywell

No matter your medical history, being told that you have multiple lung nodules can be frightening. But keep in mind that many MPNs are benign, and some may not even require treatment of any sort.

Even if your nodules are cancerous, there are almost always treatment options available. They may not be curative, but they can reduce symptoms and often extend life significantly.

Take things one step at a time and ask as many questions as you need to make a fully informed decision.

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