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 [1].  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.

Concentric circles (red arrows) seen in dermoscopy of pigmented actinic keratosis

Concentric circles (red arrows) seen in dermoscopy of lentigo maligna

Concentric circles (red arrows) seen in dermoscopy of lentigo maligna melanoma

In which lesions are concentric circles seen in through the dermatoscope?

• Lentigo maligna
• Pigmented actinic keratosis (rarely).

Concentric circles seen in dermoscopy of a lentigo maligna. Courtesy of Prof Cliff Rosendahl

Concentric circles seen in dermoscopy of a lentigo maligna on the ear

Concentric circles seen in dermoscopy of lentigo maligna on the face

Concentric circles seen in dermoscopy of lentigo maligna on the ear

Concentric circles seen in dermoscopy of pigmented actinic keratosis

Concentric circles seen in dermoscopy of a pigmented actinic keratosis on the scalp