Lung nodules are a common finding during medical imaging of the chest. These small, dense tissue masses in the lungs often appear as white spots on X-rays or CT scans. While discovering a lung nodule can be concerning, most are not cancerous and do not pose a serious health risk.
Understanding Lung Nodules
A lung nodule is typically a small, rounded or oval-shaped growth within the lung tissue. Radiologists consider a lesion a nodule if it measures less than 3 centimeters in diameter; anything larger is generally classified as a lung mass. Nodules can be solitary or multiple.
On imaging, specialists examine several characteristics to assess a nodule, including its shape, density, and calcification. A nodule might appear solid, semi-solid, or as a hazy “ground-glass” opacity. Calcification patterns, such as diffuse or popcorn-like, can indicate a benign (non-cancerous) nature.
Common Causes of Lung Nodules
Most lung nodules are benign and can develop from various factors. A common benign cause involves infectious granulomas, which are clusters of immune cells formed in response to past or current infections like tuberculosis or fungal infections such as histoplasmosis and coccidioidomycosis. Scar tissue from old infections or injuries can also appear as a nodule.
Non-infectious inflammation can also lead to nodule formation. Conditions like sarcoidosis and rheumatoid arthritis are examples of systemic inflammatory diseases that may cause lung nodules. Certain benign tumors, such as hamartomas, which are disorganized but non-cancerous growths of normal lung tissue, are another potential cause.
While less common, lung nodules can be malignant. These may include primary lung cancers or metastatic cancers that have spread to the lungs from other parts of the body. Factors such as older age, a history of smoking, and specific nodule characteristics like larger size or irregular, spiculated (spiky) borders can increase the likelihood of a nodule being cancerous.
Diagnosis and Monitoring of Lung Nodules
Lung nodules are frequently discovered incidentally during chest imaging, such as a CT scan or X-ray. Upon detection, a healthcare provider evaluates the nodule based on its appearance, size, and the patient’s medical history and risk factors for lung cancer. Small, low-risk nodules, particularly those less than 6 millimeters, often do not require immediate intervention.
For many low-risk nodules, the typical approach involves surveillance through follow-up CT scans over time, often at intervals of several months to a few years. This monitoring helps determine if the nodule changes in size or characteristics. If a nodule shows concerning features or growth, additional diagnostic tools may be utilized.
A positron emission tomography (PET) scan can assess the metabolic activity of a nodule, as cancerous cells often have higher metabolic rates. However, some inflammatory or infectious nodules can also show increased activity on a PET scan. A biopsy, taking a tissue sample, is the only definitive way to confirm if it is cancerous. Biopsies may be performed using methods like needle biopsy or bronchoscopy, guided by imaging.
Management Approaches for Lung Nodules
The management of lung nodules is determined by their assessed risk of being cancerous. For most benign or low-risk nodules, continued observation with periodic CT scans is the primary approach. If a nodule remains stable over a period, typically two years, it is generally considered benign and further follow-up may not be necessary.
When a nodule is deemed suspicious due to its size, appearance, or growth, more invasive diagnostic procedures may be considered. This could include a biopsy to obtain tissue for microscopic examination.
If a nodule is confirmed to be cancerous, treatment strategies will be developed based on the specific type and stage of cancer. These treatments can vary widely and are tailored to the individual, aiming to manage or eliminate the cancerous growth.