Possible Causes of a Lung Mass

Symptoms of a mass in your lung can include shortness of breath, back pain or chest pain (especially when you breathe deeply or cough), and unexplained weight loss. Or, it's possible that your healthcare provider says you have a lung mass, but you've had no symptoms at all so far.

Cancer is a likely reason, but benign tumors (not cancer), treatable infections, and other causes can lead to a lung mass. It's likely you'll see a pulmonary specialist (lung doctor) for more tests and diagnosis, an oncologist for cancer treatment, or other healthcare provider depending on the cause.

This article discusses lung masses and their possible causes. It explains the tests commonly used to evaluate a lung mass and make a diagnosis, as well as some of the treatment options.

Definition

A lung mass is defined as an abnormal spot or area in the lungs larger than 3 centimeters (cm), about 1.5 inches, in size. Spots smaller than 3 cm in diameter are considered lung nodules.

Size isn't the only factor, but it's a key determinant of whether a mass (or nodule) is a primary lung cancer. With respect to size:

• For nodules less than 5 millimeters, less than 1% are cancer.
• For nodules between 5 mm and 10 mm, there's up to a 28% chance that it's cancer.
• For nodules greater than 2 cm (approaching the size defined as a lung mass) the chance of malignancy is 64% to 82%.

What Can Cause a Mass in the Lung?

The most common causes of a lung mass differ from those of a lung nodule. The chance that the abnormality may be malignant (cancerous) is lower for a lung nodule than it is for a mass.

Cancer

Size isn't the only factor, but it's a key determinant of whether a mass (or nodule) is a primary lung cancer. It's important to remember that age, smoking history, environmental exposure (such as radon or asbestos), and genetics all contribute to the chance of lung cancer.

Diagnostic tests would determine the type of lung cancer. These types include:

• Non-small cell lung cancer, which accounts for 85% of lung cancers. It includes adenocarcinoma, squamous cell carcinoma, and large cell carcinomas.
• Small cell lung cancer, accounting for 10% to 15% of lung cancers
• Lung carcinoid tumors

Metastases (spread) of cancers from other regions of the body to the lung are another cause. The most common cancers that spread to the lungs are breast cancer, colon cancer, and bladder cancer.

Treatment options depend on the type and stage of the lung cancer. They can include surgery, radiation, chemotherapy, and immunotherapy drugs, with advances in recent years that have extended survival times.

What Are the Chances a Lung Mass Is Cancer?

If you have a lung mass, the most likely diagnosis is lung cancer. A history of smoking makes this even more likely. The risk also is higher among people with exposure to cancer-causing substances due to their occupation. For example, carpenters may have an elevated risk for cancers caused by wood dust.

A lung mass is more concerning if it is described as “ground glass” on an imaging report. Calcifications and cavitary shapes are more likely with benign tumors. The key factors from imaging tests include not just size, but also:

• Change in size over time (likely benign if it stays stable over two years)
• The presence of calcification or fat (certain patterns are nearly always benign)
• The characteristic of the borders or edges (margins) of the mass

The symptoms you experience, including a chronic cough, chest pain, blood-tinged sputum, and unexplained weight loss, all may suggest lung cancer. But they also are common with other lung diseases and it's important to seek a healthcare provider's accurate diagnosis.

Benign Causes

Sometimes lung masses have noncancerous causes. These benign causes are not cancer, and they will not metastasize, but some can cause serious health complications and may need to be monitored over time and/or treated.

Some benign causes of a lung mass include:

• Benign (noncancerous) lung tumors: Includes hamartoma, the most common type of benign lung tumor. People with an inherited disease known as Cowden syndrome have a greater risk for these growths.
• Lung abscesses: Infections that have been "walled off" and contained by the body
• AV malformations: Abnormal connection between arteries and veins that are usually present from birth
• Lipoid pneumonia
• Pulmonary artery aneurysms: An outpouching in the arteries that travel from the heart to the lungs can appear as a mass on imaging tests
• Amyloidosis: A build-up of abnormal proteins that form a mass

Certain fungal infections and parasitic infections also can lead to lung masses.

Diagnosis

Your healthcare provider will take a careful history and do a physical examination as part of the assessment of your lung mass.

Some of the questions your healthcare provider might ask include:

• Have you ever smoked?
• Have you traveled recently?
• What other medical conditions do you have?
• Do you have a family history of any medical problems, including lung cancer and other lung conditions?
• Have you been exposed to elevated radon levels in your home? (Radon is the second leading cause of lung cancer.)
• Are you having any symptoms, such as a persistent cough, coughing up blood, shortness of breath, lung pain, shoulder pain, back pain, or unexplained weight loss?

Depending on the results of your history and physical exam, further tests might include imaging and/or a biopsy.

Imaging

If your healthcare provider noted a lung mass on your chest X-ray, they may recommend that you have computerized tomography (CT) or magnetic resonance imaging (MRI) scan to look at the mass more closely.

These tests could help define the size and location of the mass, and sometimes make sure that the mass wasn’t an “artifact” on the X-ray—that is, something that looked like a mass but wasn’t, such as an overlap of tissues.

A positron emission tomography (PET) scan is an imaging study that detects increased metabolic activity associated with active growth. For example, a suspicious area that does not light up on a PET scan may be old scar tissue whereas an area that lights up (shows signs of increased metabolism) is more likely to be a cancerous tumor.

These tests can be especially helpful if a person has had radiation treatment for breast cancer, Hodgkin lymphoma, or lung cancer in the past—as radiation may cause scar tissue that resembles a tumor on an X-ray. They also play a key role in guiding current treatments.

Bronchoscopy

If the mass is in the central area of the lungs near the large airways, a bronchoscopy may be recommended. During a bronchoscopy, healthcare providers pass a flexible tube through your mouth and down into your bronchi.

This test can look for abnormalities in and near the large airways, and a biopsy can be performed if needed. An endobronchial ultrasound may also be done (an ultrasound that is done through the bronchi) during a bronchoscopy to better view abnormalities that are deep in the lungs and relatively close to the airways.

Fine Needle Biopsy

If your lung mass is in the outer regions of the lungs, your healthcare provider may recommend a fine needle biopsy with a needle that is placed through the chest wall and into the mass to get a tissue sample.

Lung Surgery

Sometimes it may be difficult to get a sample of the cells in your lung mass with either a needle biopsy or via a bronchoscopy. If this is the case, thoracic surgery may be recommended to get a sample of tissue.

This may be done through small incisions and using instruments with a camera (video-assisted thoracoscopic surgery), or through a traditional incision to access the lungs (thoracotomy).

The imaging and biopsy are done to provide information about the size, appearance, location, and cells in the mass.

Treatment

The treatment of your lung mass will depend on the underlying cause. If it is a primary cancerous tumor of the lung or metastatic cancer from another region of the body to the lung, treatment options may include surgery, chemotherapy, or radiation therapy.

Other less common causes of lung masses, such as infections, will be treated based on the diagnosis your healthcare provider determines after testing.

Summary

A mass in the lung can have a number of possible causes, not all of them cancer. Benign causes can include infection, aneurysm, or a congenital malformation, all with different treatment options and outlooks.

But there is an increased concern for lung cancer with a lung mass, defined as an abnormal spot that's larger than 3 cm. The chance of malignancy is greater with size, but other factors (for example, the change in size over time) are important in making a diagnosis.

Your healthcare team, including radiologists, cancer experts, and other specialists, will make the diagnosis on the basis of test results. Once a diagnosis is made, you can discuss treatment options.