Overview of SPN
A solitary pulmonary nodule (SPN) is a small, round or egg-shaped lesion (abnormal tissue) in the lungs. SPNs are typically asymptomatic, and they are usually noticed by chance on a chest x-ray that has been done for another reason. They are usually less than 3–4 cm in diameter (no larger than 6 cm) and are always surrounded by normal, functioning lung tissue.
SPNs are fairly common abnormalities on chest x-ray images: nearly one of every 500 chest x-rays shows a newly diagnosed SPN. In the United States, physicians are challenged each year by more than 150,000 new cases of SPNs.
Sixty percent of all SPNs are benign. In certain geographical areas where there are infectious agents (especially fungi) that cause SPNs, the percentage of benign SPNs increases remarkably (in some areas as high as 90 to 95 percent). Malignant SPNs may be primary Stage 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. One of the goals of diagnosis is to avoid unnecessary invasive procedures, such as surgically removing part of the lung because of a benign SPN. Benign SPNs can be treated in simpler, noninvasive ways.