Can Lung Cysts Be Cancerous?

When a lung cyst shows up on an imaging scan, it can be a source of anxiety for patients and uncertainty for physicians. Most lung cysts are benign and may never cause symptoms or health problems. However, in some cases, they can be linked to more serious conditions—including, though rarely, lung cancer. This blog explores the relationship between lung cysts and cancer, answering key questions to help you better understand what a cyst might mean for your lung health.

What Exactly Are Lung Cysts?

Lung cysts are abnormal, air-filled or fluid-filled spaces within the lung tissue. They have thin walls and can occur singly or in clusters. These cysts can form for various reasons and are often detected incidentally on chest X-rays or CT scans done for other purposes.

Cysts can be congenital (present from birth) or acquired due to infections, inflammation, or environmental exposures. While they usually don’t cause symptoms, they can sometimes lead to shortness of breath, recurrent infections, or chest pain if they enlarge, rupture, or become infected.

How Are Lung Cysts Different from Lung Cancer?

At their core, lung cysts and lung cancer are two distinct entities:

• Lung cysts are generally noncancerous, containing air or fluid with thin walls and smooth borders.
• Lung cancer is a malignant growth of abnormal cells that can spread and invade nearby tissues.

However, these two can intersect in complex ways. A cancerous tumor can:

• Develop within a pre-existing cyst
• Grow near or around a cyst
• Mimic a cyst on imaging

In these instances, distinguishing a benign cyst from a cancerous lesion can be challenging, which is why follow-up and expert imaging interpretation are crucial.

Can Lung Cancer Look Like a Cyst on a CT Scan?

Yes, and this is a key concern in modern radiology. Certain lung cancers can appear as cystic lesions on imaging—a presentation known as cyst-related primary lung malignancy or lung cancer associated with cystic airspaces (LCCA).

These types of cancers often present as:

• A thin-walled cyst that later thickens
• A cyst with a solid nodule inside
• A cyst that grows or changes shape over time

Because they don’t follow the typical pattern of solid or spiculated tumors, cystic lung cancers can be missed, especially during early lung cancer screening.

What Makes a Cyst Suspicious for Cancer?

Not all cysts require alarm—but certain red flags should prompt further investigation. These include:

• Wall Thickening: If the cyst wall becomes thick or irregular, it could indicate malignant transformation.
• Growth Over Time: A cyst that increases in size warrants close follow-up or biopsy.
• Nodular Components: Presence of a small solid mass within the cyst raises concern.
• Symptoms: Unexplained cough, blood in sputum, chest pain, or weight loss may be warning signs.
• Location and Pattern: Some locations (like upper lobes) and associated changes (e.g., nearby lymph node swelling) are more suspicious.

Radiologists and pulmonologists use these features to decide whether to observe, repeat imaging, or pursue more invasive testing.

Why Are These Types of Lung Cancer Often Overlooked?

Cystic lung cancer are often overlooked because they don’t look like traditional cancers. Instead of a solid nodule, they may appear as a simple air-filled space with subtle changes. Clinicians may assume they’re benign, especially in younger or asymptomatic patients.

Another reason is that routine lung cancer screenings focus on solid and subsolid nodules, not cysts. Without specific training or awareness, even experienced radiologists might dismiss these findings, delaying diagnosis.

However, as low-dose CT screening becomes more common, awareness of cystic cancer presentations is increasing, improving detection rates.

What Other Conditions Can Cause Lung Cysts?

Lung cysts can be caused by a wide range of non-cancerous conditions, including:

• Infections: Tuberculosis, fungal infections (like histoplasmosis), and certain bacterial pneumonias can cause cystic changes.
• Congenital Conditions: Like bronchogenic cysts or congenital pulmonary airway malformations (CPAM).
• Inflammatory Diseases: Langerhans cell histiocytosis (often in smokers) and lymphangioleiomyomatosis (LAM, more common in women).
• Mechanical Causes: Trauma or mechanical ventilation can lead to pneumatoceles (air-filled cysts).

Each of these has its own risk profile and treatment approach, which is why clinical context and additional imaging are critical for accurate diagnosis.

When Should a Lung Cyst Be Investigated Further?

Not all lung cysts require immediate action—but some do. A cyst should be further evaluated if:

• It is new or growing
• It has a thick or irregular wall
• It shows a nodule or mass inside
• The patient has risk factors (like smoking history, older age, or prior cancer)
• There are new symptoms (persistent cough, unexplained weight loss, hemoptysis)

Evaluation might include:

• High-resolution CT scan to better characterize the cyst.
• PET scan to assess for metabolic activity (cancerous lesions often show increased uptake).
• Biopsy or surgical removal if cancer is suspected or diagnosis is uncertain.

What Is the Prognosis for Cystic Lung Cancer?

Prognosis depends on several factors, including:

• Stage at diagnosis
• Tumor biology
• Patient’s overall health

Some studies suggest that cyst-related lung cancers may be more aggressive or diagnosed at a more advanced stage due to delays in recognition. However, early detection significantly improves outcomes, which is why it’s so important not to overlook subtle or atypical findings.

Treatment is typically similar to that for other lung cancers—surgery, radiation, chemotherapy, targeted therapy, or immunotherapy—depending on the specific type and stage.

Should You Be Worried If You Have a Lung Cyst?

In most cases, no. The majority of lung cysts are benign and stable over time. If you’re told you have a lung cyst, don’t panic—but do ensure it’s properly monitored.

• Stay informed about your imaging results.
• Follow up with your doctor as recommended.
• Speak up if you develop new symptoms or if you feel uneasy about the findings.

Conclusion

While the presence of a lung cyst does not automatically mean cancer, there is a rare but real possibility that it could be associated with a malignancy. With modern imaging and increased clinical awareness, we are better equipped to spot and evaluate these atypical cancers early.

If you or someone you know has been diagnosed with a lung cyst, the best next step is to work closely with a pulmonologist or radiologist to determine the appropriate level of follow-up. It could be nothing—but in the rare case it is something, early action makes all the difference.