A lung nodule is a small mass of abnormal tissue growth in the lungs. The nodules can be generally divided into benign or malignant lesions, but there are many causes for their presence in the lungs. The majority of lung nodules are benign, but the website LungNodules Organization indicates that approximately 40 percent of the lesions are malignant. Even if a lesion is benign upon initial testing, practitioners will monitor continually to check for changes in appearance that can signify malignant transformation.
Infectious Diseases
Infectious diseases of the lungs are caused by microbial invasion. These infections can result from bacteria, fungi or even be of unknown origin. Tuberculosis is an example of a bacterial infection producing lung nodules. It is caused by Mycobacterium tuberculosis bacteria, and it can be fatal if left untreated.
A fungal infection causing lung nodules is histoplasmosis. In those with pre-existing lung disease, it may present as chronic pulmonary histoplasmosis. This can lead to crippling lung conditions if not treated.
A lung abscess involves microbial invasion of unknown origin. The infection causes death of a section of the lung tissue, and nodules will form in this instance as well.
Non-infectious Disease
Non-infectious disease of the lungs does not involve any microbial invasion. Examples of non-infectious lung diseases include sarcoidosis, Wegener's granulomatosis and lung cyst. Sarcoidosis involves the formation of nodules in various organs, but it commonly starts in the lungs. The cause of sarcoidosis is unknown, and the prognosis depends on the patient's overall health and the organs affected, according to the National Heart Lung and Blood Institute. In Wegener's granulomatosis, small blood vessels become inflamed, leading to the formation of nodules called granulomas. The lung cyst forms nodules that are filled with gas or fluid.
Cancerous
The most frightening type of lung nodule is the one caused by cancer. This can be from cancer forming in the lungs or from cancer that has migrated from another area in the body. Because early treatment of a malignant lung mass is imperative, practitioners assume that all lung nodules are malignant until a benign status is proven. Regular monitoring via scans or biopsies allows the practitioner to be aware of changes in size or appearance. This is important since only malignant growths will show changes.
