How often do benign lung nodules change to cancerous, or do they all turn over a period of time?d

Generally don't turn: Key factor is change in size; benign nodules tend to stay roughly the same size over time, malignant nodules don't-they get bigger more rapidly. Benign nodules are common-aftermath of prior infection, inflammation, etc. Smoker? Ex- smoker? Lived/worked with a smoker? Occupational exposures? Family history? All are factors to be considered. Get follow up with your md, and/or pulmonary specialist.

Not always: Cancers are known to arise from underlying inflammation and scar tissue; it is possible to develop cancerous growth in scar/benign lung nodules, however this is not common; "benign" lung nodules have to be followed by serial scans to monitor change in size and radio-graphic characteristics.