A lung nodule is a small growth or spot that appears in the lung. These nodules are common and are often discovered by chance during medical imaging performed for other reasons. While finding a lung nodule can be concerning, most of them are not cancerous.
Understanding Lung Nodules
A lung nodule is a small, round or oval-shaped growth in the lung, generally measuring less than 3 centimeters (about 1.2 inches) in diameter. Growths larger than this size are usually referred to as a lung mass, which has a higher probability of being cancerous. On imaging scans, a lung nodule typically appears as a white spot.
Small lung nodules typically do not cause symptoms, meaning individuals are often unaware they have one. However, if a nodule is large or pressing on an airway, it might lead to symptoms like a persistent cough, shortness of breath, or chest pain.
Detection of Lung Nodules
Lung nodules are most commonly discovered incidentally during imaging tests, such as chest X-rays or CT scans, performed for unrelated medical reasons. For example, a nodule might be seen during a scan for a routine check-up or an assessment of other symptoms. Chest X-rays provide basic images of the lungs, while computed tomography (CT) scans offer more detailed, cross-sectional views.
Sometimes, nodules are also found during lung cancer screening programs, particularly for individuals at high risk due to factors like smoking history. Regardless of how they are found, further evaluation is often recommended to understand the nature of the nodule.
Causes of Lung Nodules
Lung nodules can arise from various factors, categorized as benign or malignant.
Common benign causes include infections, inflammation, and scar tissue. Infections, such as fungal infections (e.g., histoplasmosis, coccidioidomycosis) or bacterial infections like tuberculosis and pneumonia, can lead to the formation of granulomas, which are small clusters of immune cells that appear as nodules. Inflammatory conditions, including autoimmune diseases like sarcoidosis and rheumatoid arthritis, can also cause nodules. Old infections or injuries can leave behind scar tissue that may resemble a nodule on imaging.
While less common, lung cancer is a serious cause of lung nodules, either as a primary tumor or as a result of cancer spreading from other parts of the body (metastatic cancer). Several characteristics seen on imaging can help differentiate between benign and malignant nodules, though a definitive diagnosis often requires further testing. Factors suggesting the possibility of malignancy include larger size (especially over 10 mm), irregular or spiculated (spiky) margins, and a faster growth rate. Benign nodules often have smooth, round shapes and may contain specific patterns of calcification (calcium deposits) that indicate a non-cancerous origin. Patient history, such as smoking, age, and family history of lung cancer, also plays a significant role in assessing the risk.
Managing Lung Nodules
The management approach for a lung nodule depends on its characteristics and the individual’s overall health and risk factors. If a nodule appears to be benign based on its size, shape, and the patient’s low risk for cancer, a “watchful waiting” approach is often adopted. This typically involves scheduling follow-up CT scans at regular intervals, such as every 3, 6, or 12 months, to monitor for any changes in the nodule’s size or appearance. If the nodule remains stable over a period, often two years, it is generally considered benign and may require no further action.
If a nodule is larger, has suspicious features, or if the patient has a higher risk of malignancy, further diagnostic tests may be recommended. A Positron Emission Tomography (PET) scan can be used to assess the metabolic activity of the nodule; cancerous cells tend to be more metabolically active and “light up” on a PET scan. However, some benign conditions like infections can also show increased activity. A biopsy, which involves taking a tissue sample from the nodule, provides a definitive diagnosis. Biopsies can be performed using various methods, including needle biopsies guided by imaging, or bronchoscopy, where a thin tube is inserted into the airways to reach the nodule. If a nodule is confirmed to be malignant, treatment options may include surgery to remove the nodule, radiation therapy, or chemotherapy, depending on the specific type and stage of cancer.