Not everyone has small nodules in the lungs, due to the fact that some people can be found to have small nodules in the lungs through imaging tests including X-rays, CT, and MRI, which are mainly seen as a result of lung lesions. The vast majority are commonly found in benign lung lesions such as inflammatory pseudotumors. They are caused by pathogenic infections that result in varying degrees of fibrosis and calcification of the lungs, such as tuberculosis, fungal pneumonia, and idiopathic interstitial fibrosis of the lungs. Rarely, they are seen in malignant tumors of the lungs, such as bronchopulmonary carcinoma and alveolar cell carcinoma, and may have small nodules in the lungs. The nature of the nodules can be clarified by taking biopsies for pathologic examination.