The high content of air in the lungs gives them a nearly transparent appearance on chest X-rays and CT scans. In contrast, areas of solid tissue within the lungs appear as white spots with these imaging techniques. A spot on the lung is an abnormal finding, which requires further evaluation to determine the cause of the lung mass. Inflammatory reactions, congenital malformations and cancerous or noncancerous growths may cause radiographic lung spots. Distinguishing cancerous from noncancerous masses remains the utmost concern.
Early Stage Lung Cancer
A spot on the lung may represent early stage lung cancer. Accurately diagnosing the disease in its early stages provides the opportunity for potentially curative intervention. Advancing age and current or former smoking increase the probability of a pulmonary nodule proving cancerous. The American College of Chest Physicians' clinical practice guidelines on the evaluation of pulmonary nodules notes that the overwhelming majority of cancerous lung spots represent non-small cell lung cancer, with adenocarcinomas and squamous cell carcinomas predominating.
Granulomas
Granulomas consist of walled-off masses of inflammatory tissue, which appear as lung nodules on chest X-ray and CT scan images. Chronic lung infections including tuberculosis, histoplasmosis, coccidioidomycosis, cryptococcosis and blastomycosis often cause lung granulomas. Dr. Edward Rosenow III of the Mayo Clinic states that histoplasmosis proves the most common cause of lung granulomas in the United States. The National Lung Health Education Program reports that granulomas remain the most frequent cause of noncancerous pulmonary nodules.
Hamartomas
Hamartomas are noncancerous growths comprised of a mixture of different cells from the lungs. Cartilage, fat and connective tissues commonly constitute lung hamartomas. These noncancerous growths represent the most common noncancerous tumors of the lungs. In a review article on pulmonary nodules published in the journal "Chest," Dr. Michael Gould and colleagues report that hamartomas represent approximately 15 percent of all noncancerous pulmonary nodules.
Bronchogenic Cysts
Bronchogenic cysts are noncancerous congenital lung malformations, which may present as incidental pulmonary nodules. The cysts appear as circumscribed, fluid-filled masses on chest X-rays and CT scans. They most commonly occur toward the center of the chest, but may grow in the outer areas of the lungs. The National Lung Health Education Program notes that bronchogenic cysts are an uncommon cause of radiographically detected pulmonary nodules.
Hemangiomas and Arteriovenous Malformations
A hemangioma represents a noncancerous mass of aberrantly growing blood vessels. An arteriovenous malformation similarly represents a blood vessel malformation in which an abnormal connection exists between the arterial and venous circulation. The American College of Chest Physicians' clinical practice guidelines on the evaluation of pulmonary nodules points out that hemangiomas and arteriovenous malformations remain possible causes of lung spots on radiographic images.
