What it means
Circumscribed means having a clear outline. A well-circumscribed lump has a crisp edge all the way around, so the radiologist can see exactly where it ends and normal tissue begins. This often suggests it pushes gently against nearby tissue rather than growing into it. The opposite is ill-defined, meaning the edges are blurry.
When it matters
Smooth, sharp edges are one of the features that make a finding more likely to be harmless. Simple cysts, harmless breast lumps called fibroadenomas and many lymph nodes look this way. Still, it is not proof on its own, because some cancers, including some that have spread from elsewhere, can also have clear edges. Radiologists weigh the edges with size, contents and change over time.
Questions to ask your doctor
- Do the clear edges make this finding more likely to be harmless?
- Are there other features that still need checking?
- Does it need a follow-up scan to make sure it stays the same?
