Common Causes of Multiple Lung Nodules

Having multiple lung nodules means 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.

What Are Multiple Lung Nodules?

Having multiple lung nodules means there are more than one nodule in your lungs. While these nodules can be cancerous, they are more often benign rather than malignant.

Non-cancerous lung nodules can form after there has been inflammation of some kind in the lung. These nodules start as a small clump of cells called a granuloma. Over time, the granuloma can harden or “calcify,” forming a lung nodule. 

A cancerous lung nodule forms when cells develop changes or mutations. These changes sometimes happen for unknown reasons and are sometimes related to previous damage caused by something you inhaled, such as cigarette smoke. The changes cause the cells to begin multiplying abnormally, forming a tumor. Cancerous nodules in the lung can also form when cancer cells spread to the lungs from a primary tumor in another part of the body (metastasis).

Causes

Multiple lung nodules can result from either benign (non-cancerous) or malignant (cancerous) conditions. Below are some of the most common causes of lung nodules.

Benign Lung Nodules

There are more benign causes of multiple lung nodules than malignant ones.

• Mediastinal lymph nodes are found along the lining of the lung. Like other lymph nodes, they can enlarge during infections, sometimes appearing 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 occur 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.

Cancerous Lung Nodules

Diagnosis

Most lung nodules do not cause any symptoms. Although some people do experience coughing and wheezing or shortness of breath, many only find out they have lung nodules when they’re seen on a scan.

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 whenever there are multiple lung nodules seen on a scan. Although lung nodules are more likely to have one of many different benign causes, cancer is still the single most common cause of multiple lung nodules.

The way that the nodules look on a scan can give providers hints about which type they are.

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.

Cancerous lung nodules are more likely to be metastatic, meaning they spread to the lungs from somewhere else in the body. 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 the following:

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:

• Nodules related to metastatic breast cancer can be treated with a combination of a lumpectomy or mastectomy, radiation therapy, chemotherapy, endocrine therapy, and newer targeted drugs like Ibrance (palbociclib).
• Nodules related to metastatic colon cancer might be treated with a colon resection accompanied by chemotherapy and targeted drugs like Avastin (bevacizumab).
• Primary cancers like lymphoma that produce multiple lung nodules may require chemotherapy, radiation therapy, biologic therapy, immunotherapy, stem cell transplantation, CAR T-cell therapy, or a combination of these treatments.
• Newer techniques such as stereotactic body radiotherapy (SBRT) can be used to treat a single metastasis and, sometimes, multiple metastases. If there are just a few of them, treating the malignant nodules may improve a patient’s survival.