A computed tomography (CT) scan uses a series of X-ray images from various angles to create detailed cross-sectional views of the body. For the lungs, this technology produces sectional images that offer a more detailed view than conventional X-rays. CT scans serve as a primary tool for detecting lung abnormalities, including potential cancers, often before symptoms become apparent. This non-invasive procedure provides precise information about soft tissues, organs, bones, and blood vessels.
Identifying Potential Abnormalities on a Lung CT Scan
On a CT scan, healthy lungs appear as dark spaces due to air’s low density. Within this dark background, thin white lines of blood vessels and airways are visible, forming a uniform pattern. Radiologists look for deviations from this normal appearance, which can indicate an abnormality.
A common finding is a pulmonary nodule, which appears as a small, rounded or irregular white spot. These nodules are distinct from the surrounding lung tissue. When an abnormality is larger, it is classified as a lung mass. Other visual cues include ground-glass opacities, which are hazy areas of increased lung density. Enlarged lymph nodes may also appear in the chest as larger, often rounded, structures.
Characteristics of Malignant vs. Benign Lung Nodules
Distinguishing between a malignant (cancerous) and benign (non-cancerous) lung nodule on a CT scan involves evaluating several specific characteristics. While a CT scan cannot definitively diagnose cancer—a biopsy is required for that—certain features can strongly suggest malignancy or benignity. Malignant nodules may display irregular or “spiculated” borders, indicating invasive growth into surrounding tissue. Their shape might also appear lobulated or bumpy, rather than smooth. Rapid growth over time, such as a doubling in size between 30 and 400 days, suggests malignancy, while stability over two years suggests a benign nature. Malignant nodules also tend to be larger, with those exceeding 8 millimeters (about 0.3 inches) having a higher probability of being cancerous.
Conversely, benign lung nodules often have smooth, regular borders and a more uniform, round, or sometimes polygonal shape. A strong indicator of benignity is the presence of calcification within the nodule, especially if it’s diffuse, central, laminated (layered), or appears “popcorn-like”. These calcifications often result from old inflammation or infections. Benign nodules are often smaller, with those less than 6 millimeters (about 0.24 inches) having a very low likelihood of being cancerous, and are often homogeneous in appearance. The presence of macroscopic fat within a nodule also reliably indicates a benign hamartoma.
Understanding Your CT Scan Report
Your CT scan report is a written document from the radiologist detailing the findings from your imaging. It uses specific terminology to describe any detected abnormalities. A “pulmonary nodule” refers to a small, rounded spot in the lung, less than 3 cm in diameter. If the spot is larger than 3 cm, it is called a “mass”. “Spiculation” describes a nodule with jagged, pointed margins, which can raise suspicion for malignancy.
“Ground-glass opacity” (GGO) indicates a hazy, increased density in the lung where blood vessels and airway structures are still visible through the opacity. This appearance can be associated with various conditions, including inflammation, infection, or certain types of early lung cancer. “Mediastinal adenopathy” means enlarged lymph nodes in the mediastinum, the central compartment of the chest. The report may also include a Lung-RADS score, a standardized classification system that helps categorize the risk of cancer and guide further management. This score ranges from 0 (incomplete study) to 4 (highly suspicious for malignancy), with subcategories providing more specific risk estimates. For example, a Lung-RADS 1 or 2 indicates a very low likelihood of cancer (less than 1%), while a Lung-RADS 4A or 4B signifies a higher risk (ranging from 5% to over 15%).
Next Steps After a Suspicious Scan
If a CT scan reveals a suspicious finding, such as a nodule or mass, several follow-up actions may be recommended. One common approach is “watchful waiting,” where the nodule is monitored with repeat CT scans over time to observe any changes in size or characteristics. The frequency of these follow-up scans depends on factors like the nodule’s size, density, and the patient’s risk profile; smaller, less suspicious nodules might be re-scanned annually, while larger or more concerning ones may require scans every three to six months.
Further imaging may be suggested, such as a positron emission tomography (PET) scan. A PET scan assesses the metabolic activity of the nodule, as cancerous cells have higher metabolic rates and may appear brighter on the scan. This can help differentiate between active cancer and benign growths, particularly for nodules 8 millimeters or larger. If the nodule continues to be suspicious or shows concerning features like rapid growth, a biopsy may be performed. This procedure involves obtaining a tissue sample from the nodule, often guided by CT imaging or bronchoscopy, for definitive microscopic analysis to confirm or rule out cancer.