Background

A focus on the issue of Lung nodules given I see these mentioned all the time in my online patient group, on many occasions by a worried newly diagnosed patient who has just been told this was found during diagnostic scans.  Sometimes a lung nodule is also called a ‘pulmonary’ nodule and the two phrases mean the same thing.

A lung nodule is an abnormal growth that forms in a lung. You may have one nodule on the lung or several nodules. Nodules may develop in one lung or both. Most lung nodules are benign (not cancerous). Only rarely, lung nodules are a sign of cancer in the lung.  They can show up on imaging scans like X-rays or CT scans and are only found when doctors are checking for something else (i.e. they are incidental findings).

How common are lung nodules?

Lung nodules are very common. According to UK NHS, around 35% of people have them. Some US healthcare providers (e.g. Cleveland Clinic) put it at 50% of the adults who get either a CT scan or an x-ray.

Clearly, when you already have a cancer diagnosis, the discovery of more issues on top of that is of concern to patients and their families. As inferred above, many are incidental and only found because of imaging during an investigation of something else, e.g. a cancer diagnosis.  But it’s really important to remember that most lung nodules aren’t cancerous and don’t require treatment. A noncancerous lung nodule shouldn’t affect your quality of life.

What can cause a Lung (Pulmonary) Nodule?

According to Cleveland Clinic, when infection or illness inflames lung tissue, a small clump of cells (granuloma) can form. Over time, a granuloma can calcify or harden in the lung, causing a noncancerous lung nodule.

Other causes of noncancerous lung nodules include:

• Air irritants or pollutants.
• Autoimmune diseases, such as rheumatoid arthritis and sarcoidosis.
• Fungal infections like histoplasmosis.
• Respiratory system infections, such as tuberculosis (TB).
• Scar tissue.

The vast majority of lung nodules will be noncancerous (benign) but a small risk of lung nodules being an early stage of cancer remains.  Thus, why when a patient is diagnosed with a lung nodule, it is most important to rule out cancer in the lung.

Risk Factors

There are several factors that may increase the risk of having cancer. Anyone can develop pulmonary nodules. According to Cleveland Clinic, a nodule is more likely to be cancer if you:

• If you are a former or current smoker
• Are older than 65.
• Have a family history of cancer.
• Received radiation therapy to the chest.
• Had exposure to asbestos, radon, or secondhand smoke.

Evaluating a Lung Nodule

Doctors and specialist nurses look at the size of the nodule and the characteristics of its appearance. Not all lung nodules require more follow-up. Can a CT scan tell if it is cancerous?  According to CCTA, the short answer is no. A CT scan usually isn’t enough to tell whether a lung nodule is a benign tumor or a cancerous lump. A biopsy is the only way to confirm cancer.  But the nodule’s characteristics as seen on a CT scan may offer clues.  To determine whether the likelihood of lung cancer is high or low, physicians usually look at three distinct characteristics of the nodule: the size of the spot, its shape, and whether the nodule is calcified.

• If the CT scan shows small nodules (less than a centimeter wide, or about the size of a green pea), the probability of them being cancerous is low. Larger nodules are more worrisome.
• Rounded nodules are less likely to be cancerous than spiculated (having jagged edges) ones.
• Calcified lung nodules contain calcium deposits that sometimes form in response to infection. These nodules are most likely noncancerous.

Another key sign physicians look for when trying to determine whether a lung nodule may be cancerous is the difference in the size of the nodule between one scan and another taken at a later time. Cancerous nodules are more likely to grow thus why a short period of surveillance is often required. 

So, while a CT scan can’t confirm whether your lung nodule is cancerous, it may determine whether further imaging tests are warranted. If this is the case, your doctor may order further specialised imaging and/or a biopsy of the compromised lung tissue.

Healthcare systems will have guidelines to deal with lung nodules via clinical studies of thousands of people’s scans and their outcomes.  The risk factors above and your own clinical history will also be taken into account.

It is not always possible to tell what a nodule represents on the very first scan. When you are already under surveillance for cancer, checks on lung nodules can be undertaken as part of that surveillance.  In a personal example, my own lung nodule was incidentally found in 2010 (approx. 2-3mm).  12 years and many scans later, it remains the same size.

In fact, most lung nodules stay the same size, get smaller, or even disappear. If the nodule has not increased in size over several scans, no more surveillance will be required but opportunistic checks via scans for other conditions may be done.  So those reading this with Neuroendocrine Cancer, be assured they will keep an eye on this issue.

Biopsies. Your provider may choose to biopsy the nodule to rule out cancer if you are a smoker, you have other symptoms of lung cancer, or the nodule has grown in size or has changed when compared to earlier images. If a biopsy is required, this may require some specialised imaging for planning followed by lung biopsy methods such as bronchoscopy or CT-guided biopsy.  

Summary

I hope this has been useful for those who have been told they have a lung/pulmonary nodule.  It would seem for most; this is a minor and low-risk issue.