I lung cancer tumors or metastases from other parts of the body. Determining the malignancy of an SPN is an integral and challenging part of diagnosis. Benign SPNs can be treated in simpler, noninvasive ways. SPNs should be considered potentially cancerous until proven otherwise. For example, in the United States, histoplasmosis is more prevalent in the Ohio River Valley, especially Tennessee and Kentucky, than in other parts of the country.
Blastomycosis is more common in the upper Midwest.
Many people who harbor fungi that can cause SPNs never actually develop an SPN or other respiratory symptoms. Patients with weakened immune systems due to disease, surgery, etc. are at greater risk for developing infectious SPNs. Patients with chronic lung disease are at an increased risk for fungal infections that can cause SPNs. Certain occupations, such as bridge building and farming, are associated with exposure to fungi that can lead to SPNs. A history of extensive asbestos exposure has been linked to the development of malignant solitary pulmonary nodules.