Infections, as well as disorders such as sarcoidosis, Wegener's granulomatosis and rheumatoid arthritis, may cause spots on the lung, known as pulmonary nodules, according to Cleveland Clinic. Benign or malignant neoplasms or malignant tumors, including lung cancer, lymphoma, sarcoma and metastatic tumors, can also cause pulmonary nodules.
Infections such as mycobacterium tuberculosis and mycobacterium avium intracellulare can cause pulmonary nodules, as can fungal infections such as aspergillosis, coccidiomycosis and cryptococcosis, notes Cleveland Clinic. Inflammation related to these infections often causes pulmonary nodules known as granulomas that may become calcified over time.
Neoplasms that cause pulmonary nodules include lumps of connective tissue known as fibromas, lumps of nerve tissue known as neurofibromas and hamartomas, which are groupings of normal cells that have attached abnormally, according to Cleveland Clinic. Malignant tumors that cause spots on the lung include lymphoma, a cancer that originates in the immune system, metastatic tumors that started in another part of the body and traveled to the lungs, and tumors in connective tissue known as sarcomas. Non-small cell is the most common type of lung cancer that causes pulmonary nodules, though small cell cancer and lung carcinoid tumors can also cause them, according to the American Cancer Society.