What are concentric circles?
Concentric circles are a specific clue to melanoma on the face (lentigo maligna), but the clue has poor sensitivity as they are rarely present. In a study by Tschandl et al, concentric circles were only found in 4.2% of flat facial melanomas, usually larger lesions . Concentric circles are also referred to as a circle within a circle and the isobar sign.
What do concentric circles look like through the dermatoscope?
Concentric circles consist of an asymmetrical pigmented follicular opening with a darker dot located within ostial openings.
In which lesions are concentric circles seen in through the dermatoscope?
- Lentigo maligna
- Pigmented actinic keratosis (rarely).