A lung nodule is a small, abnormal growth or spot that appears on the lung, often detected during imaging tests like X-rays or CT scans. These findings are common, occurring in up to half of adults who undergo chest scans for various reasons. While the presence of a spot on the lung can be concerning, most lung nodules are not cancerous.
What Are Benign Lung Nodules?
Benign lung nodules are non-cancerous growths. These nodules are typically the result of the body’s response to past infections or inflammation. Common causes include granulomas, which are small clumps of immune cells formed after infections like tuberculosis or fungal infections such as histoplasmosis or coccidioidomycosis.
Benign nodules can also arise from inflammatory conditions like rheumatoid arthritis or sarcoidosis, or they can be benign tumors such as hamartomas. On imaging, benign nodules often display characteristics like a smooth, round shape, stable size over time, and the presence of calcification, which indicates hardened calcium deposits. Most individuals with benign lung nodules do not experience symptoms, as they are typically discovered incidentally during scans for other medical reasons.
Growth in Benign Lung Nodules
Benign lung nodules can grow. While many remain stable, some may increase in size due to non-cancerous reasons. This growth can be attributed to ongoing or resolving inflammation within the lung tissue. For example, an active but non-cancerous infection could cause a nodule to enlarge as the body continues its immune response.
Certain types of benign lesions, such as hamartomas, can also exhibit slow, natural growth over time. Not every instance of nodule growth signals malignancy. Minor, slow, or even fluctuating changes in size can still be consistent with a benign nature, distinguishing them from the typically more rapid and continuous growth patterns seen in cancerous nodules. Cancerous nodules, for instance, may double in size every four months on average, or even as quickly as 25 days.
Monitoring and Evaluation of Nodule Changes
When growth is observed in a lung nodule, healthcare providers monitor these changes, often through follow-up imaging like CT scans. These scans help track the nodule’s size, shape, and characteristics over time. A nodule that remains stable for at least two years is generally considered benign, particularly for solid nodules.
However, certain patterns of growth or specific characteristics might prompt further investigation. Rapid growth, the appearance of new solid components within a previously non-solid nodule, or an irregular, bumpy, or spiky shape can raise concern. If such concerning features are noted, additional diagnostic steps may be recommended. These could include a PET scan to assess the nodule’s metabolic activity, or a biopsy, where a tissue sample is taken for microscopic examination to determine its nature.