Histoplasmosis

• One cause in the formation of lung nodules is a condition called histoplasmosis. The development of histoplasmosis is directly linked to a fungus known as Histoplasma capsulatum. When you are exposed to this particular pathogen, it is possible for you to inhale the spores into the lungs, causing an infection. This infection can cause noncancerous nodules to form in the lungs. But these nodules, as well as the condition itself, don't normally produce any symptoms of infection, so most people go unaware of the condition.
  
  

Tuberculosis

• Lung nodules can also be caused by tuberculosis (TB), an infectious disease caused by the airborne pathogen Mycobacterium tuberculosis. As you talk, breathe, cough or sneeze, you release moisture into the air. Each of us comes into contact with this moisture every day. But if this moisture is from someone infected with tuberculosis, a potential for inhaling the pathogen into our lungs manifests and can result in an infection. As we suffer from this TB infection, noncancerous nodules may begin to form within the lungs. And much like histoplasmosis, most people are unaware that they are suffering from the infection because TB doesn't always cause symptoms.
  
  

Hematoma

• Another cause of lung nodules is the formation of a hematoma within the lungs. Like a bruise, a hematoma forms from some sort of injury or irritation that causes blood to pool and the area to swell. But unlike the impact or stress that causes a bruise to form, a hematoma within the lung is usually a result of some sort of infection that irritates the lungs. Once a hematoma forms, it can cause a noncancerous nodule to stick out from the lining of the lungs.
  
  

Lung Cysts

• Lung cysts are essentially small lesions that develop from pneumonia, pulmonary metastasis and other medical conditions. When these lesions fill with fluid or air, they are seen as nodules in the lungs. Depending on the condition, these nodules may or may not be cancerous.
  
  

Vascular Abnormalities

• It is also possible for the nodules to be caused by some sort of vascular abnormality within the lungs. A vascular abnormality is an aneurysm, embolus (pulmonary obstruction), hemorrhage or hyperemia (congestion of the lung) that may trigger the formation of a nodule. These nodules are almost always noncancerous and cause no issues for the individual.
  
  

Lung Cancer

• Though not as common as the other condition, a lung nodule may also be a result of lung cancer. In this situation, abnormal cells cause a cancerous nodule to form within the lining of the lung. The nodule would be treated within the same medical procedures as the lung cancer itself.