Lung Mass
A lung mass is a focal area of abnormal tissue in the lung that measures larger than about 3 centimeters. (Smaller, round areas are usually called nodules.) Lung masses can be caused by a wide range of conditions, including infections, inflammation, benign growths, and lung cancer. Imaging—particularly CT of the chest—is essential for evaluating a lung mass, characterizing its features, and guiding further testing. Many lung masses turn out to be benign, but some are cancerous, so prompt and careful evaluation is important.
What is it?
A lung mass is a focal area of abnormal tissue in the lung that measures more than about 3 centimeters across. Smaller round abnormalities (under 3 cm) are generally referred to as pulmonary nodules, while larger ones are called masses. The distinction matters because larger size is generally associated with a higher likelihood of malignancy, although many lung masses still turn out to be benign.
Lung masses can arise from a wide variety of causes. Malignant causes include primary lung cancers such as adenocarcinoma, squamous cell carcinoma, small cell lung cancer, and large cell carcinoma, as well as less common tumors such as carcinoid tumors and certain sarcomas. Lung metastases from cancers that started elsewhere in the body (for example, breast, colon, kidney, or melanoma) can also appear as masses. Benign causes include infections such as bacterial or fungal pneumonia, tuberculosis, abscesses, and certain parasitic infections; inflammatory conditions like sarcoidosis, vasculitis, and rheumatoid nodules; benign tumors such as hamartomas; and other findings such as rounded atelectasis, prior scarring, or vascular abnormalities. The specific cause cannot usually be determined from imaging alone; the patient’s age, smoking history, occupational and environmental exposures, prior cancer history, infectious risk factors, and overall medical context all play a role.
Symptoms depend on the size, location, and underlying cause of the mass. Many lung masses cause no symptoms and are discovered incidentally on a chest X-ray or CT performed for other reasons. When symptoms occur, they may include a persistent cough, coughing up blood (hemoptysis), shortness of breath, chest pain, recurrent pneumonia in the same area, hoarseness, unintended weight loss, fatigue, or, in advanced cases, symptoms from spread of disease to other organs. Smoking history, prior cancer, exposure to asbestos or radon, and a family history of lung cancer can raise the likelihood that a mass is malignant, although these factors are not used in isolation.
CT of the chest is the primary imaging test for evaluating a lung mass because it provides detailed information about size, shape, margins, density, internal characteristics (such as calcification or cavitation), and relationship to nearby structures including blood vessels, airways, the chest wall, and mediastinum. Imaging features sometimes suggest a more likely cause, but most lung masses ultimately require tissue sampling for a definite diagnosis. PET/CT helps assess metabolic activity and look for evidence of spread elsewhere in the body. MRI is used in selected cases, such as evaluation of chest wall or brain involvement. Bronchoscopy and image-guided biopsy (usually CT-guided) are commonly used to obtain tissue for pathologic diagnosis. Depending on the situation, additional studies such as pulmonary function testing and laboratory tests may also be performed.
Important to Know
Evaluation and treatment of a lung mass are highly individualized and depend on the suspected cause, the size and location of the mass, the patient’s overall health, and the results of further testing. Once a mass is identified, the goal is to determine whether it represents cancer or another condition, and to do so efficiently. This usually involves a combination of imaging, biopsy, and consultation with specialists such as pulmonologists, thoracic surgeons, interventional radiologists, and oncologists.
When malignancy is confirmed, treatment depends on the specific type of cancer and its stage, and may include surgery, radiation, chemotherapy, immunotherapy, or targeted therapy. When a benign cause is found, treatment is directed at that specific condition (for example, antibiotics for an infection or anti-inflammatory therapy for certain inflammatory conditions). In some cases, when imaging features strongly suggest a benign process and the patient is at low risk, follow-up imaging over time may be appropriate to confirm stability.
Because the differential diagnosis is broad and the stakes can be high, prompt evaluation and clear communication with a physician are essential whenever a lung mass is identified.
Red flag symptoms include coughing up blood, severe shortness of breath, chest pain (especially with breathing), fever and chills with worsening cough, significant unintended weight loss, new severe headache or neurological symptoms in someone with a known or suspected lung mass, or rapidly worsening fatigue. These warrant prompt medical evaluation.