The discovery of an abnormal spot on a chest X-ray or CT scan, often referred to as a lung lesion, can cause immediate concern. A lung lesion describes an unusual area of tissue appearing on an imaging study. These findings are often incidental, meaning the scan was performed for an unrelated reason, such as routine screening or evaluation of a cough. While the presence of any abnormal growth is unsettling, the majority of these lesions are not cancerous. The evaluation process focuses on differentiating between the many benign possibilities and the less common, malignant ones.
Defining Lung Lesions and Nodules
A lung lesion is a general description for any area of abnormal tissue, but physicians use precise size classifications to guide evaluation. A “pulmonary nodule” is a lesion measuring up to three centimeters (about 1.2 inches) in diameter. These nodules are common, frequently found in up to half of all adults who undergo a chest CT scan.
A lesion exceeding three centimeters is classified as a “pulmonary mass.” This size distinction is significant because a mass has a higher probability of being malignant compared to a smaller nodule. Lesions are also categorized by their appearance on the scan, such as whether they are solid, partially solid, or have a hazy, non-solid ground-glass opacity. This terminology helps define the initial level of concern and the necessary follow-up protocol.
Understanding the Range of Potential Causes
The causes for lung lesions span a wide spectrum, with most relating to past infections or non-cancerous tissue growth. Many small nodules are benign lesions, often representing scar tissue from a previous inflammatory process. A common benign cause is a granuloma, a clump of immune cells and scar tissue left behind by fungal infections (like histoplasmosis) or bacterial infections (such as tuberculosis). Benign tumors, like hamartomas, are also frequent findings resulting from a localized overgrowth of normal lung tissue components.
Lesions can also be caused by active infectious and inflammatory processes. An acute pneumonia or a fungal lung infection can create a lesion that mimics a nodule on a scan. Certain autoimmune diseases, such as rheumatoid arthritis or sarcoidosis, can also manifest as nodules or masses. These findings usually resolve or remain stable once the underlying inflammatory condition is managed.
The most concerning cause is malignancy, which includes primary lung cancer or metastatic cancer spread from another part of the body. Lesions that are larger, have irregular or spiculated (spiky) borders, or exhibit rapid growth are associated with a higher risk of being cancerous. A patient’s history, including age, heavy smoking, or prior cancer diagnosis, increases the probability that the lesion is malignant. Conversely, specific patterns of calcification within the lesion suggest a high likelihood of a benign origin.
The Process of Evaluating a Lung Lesion
Following the discovery of a lung lesion, the first step is a thorough risk assessment based on the patient’s clinical history and the lesion’s appearance on the initial CT scan. Factors like smoking history, advanced age, and previous cancer diagnoses are weighted against imaging characteristics such as nodule size and shape. This process helps assign a probability of malignancy, guiding the subsequent investigative path.
For small, low-risk nodules, the standard approach is “watchful waiting,” involving serial follow-up CT scans. These scans are performed at routine intervals, typically every six to twelve months for up to two years, to monitor for any change in size. A lesion that remains stable for two years is considered benign and requires no further investigation.
If the lesion is larger, has suspicious features, or is found in a high-risk patient, advanced imaging studies are utilized. A Positron Emission Tomography (PET) scan measures the metabolic activity of the lesion. Highly active cells, such as those in aggressive cancers, tend to absorb more of the injected radioactive tracer. A bright spot on a PET scan suggests high metabolic activity and an increased likelihood of malignancy, while low uptake suggests a benign process.
When the risk of malignancy is high or the diagnosis remains unclear, a tissue sample is required to confirm the cellular makeup. Biopsies are performed using different techniques depending on the lesion’s location. A fine-needle aspiration, often guided by a CT scan, is used for lesions near the edge of the lung. A bronchoscopy allows access to lesions closer to the central airways, and the definitive diagnosis is made by a pathologist.
Management and Treatment Options
The management plan for a lung lesion is determined by the definitive diagnosis established through the evaluation process. Lesions confirmed to be benign, such as stable granulomas or hamartomas, typically require no active treatment. The patient is often discharged from surveillance unless the lesion is causing symptoms.
If the lesion is caused by an active infection or an inflammatory disorder, treatment focuses on resolving the underlying condition. This may involve antibiotics for a bacterial infection, antifungal medications for a fungal infection, or immunosuppressive therapy for an autoimmune disease. Once the primary illness is treated, the lesion is expected to shrink or disappear.
For lesions diagnosed as malignant, treatment aims to remove or destroy the cancerous cells. Early-stage lung cancer is often managed with surgical removal of the nodule and a portion of the surrounding lung tissue. For patients who cannot tolerate surgery, high-dose, precisely targeted radiation therapy, known as stereotactic body radiation therapy (SBRT), can be an effective alternative. Advanced or metastatic cancers are generally treated with systemic therapies, including chemotherapy, targeted therapy, or immunotherapy.