What it means
A small rounded lump of tissue, usually under about 3cm. Larger than that and it tends to be called a mass.
Nodules are extremely common and the overwhelming majority are harmless.
- Lung nodules — usually old infections or scars. Found routinely on CT scans done for other reasons
- Thyroid nodules — present in a large proportion of adults, and the great majority are benign
- Skin nodules — cysts, lipomas and similar
Size, edges and whether it changes over time matter far more than its existence.
In practice
On CT, ultrasound and X-ray reports, and increasingly through lung cancer screening, where nodule detection is the commonest abnormal result.
Often with a recommendation for a repeat scan at three, six or twelve months.
Why it matters
Follow the recommended interval, and make sure someone is actually booking it. Nodule follow-up is the single easiest thing to lose between services.
Ask how it compares with any previous scan. A nodule that has been unchanged for two years is a very different thing from a new one.
Try not to spend the interval assuming the worst. Most nodules never turn out to be anything, and the repeat scan exists because watching is safer than intervening.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026