It is the pattern of facial skin, but also not unusual at other locations on the body.
On the face, they are formed by melanin pigment arranged either around the openings of the crater-like infundibula or in infundibular epithelium. The center of the infundibulum appears hypopigmented. If infundibula contain keratinized material the hypopigmented center is seen as a yellow or orange clod. Circles may be brown, gray or black.
- Brown circles: solar lentigo or flat seborrheic keratosis.
- Gray circles on facial lesions: melanoma in situ.
- Differential diagnoses: lichen planus-like keratosis, pigmented actinic keratosis, in situ melanoma.
- On the trunk or the extremities the pattern of circles may be a variant of the reticular pattern.
- Differential diagnoses: junctional Clark nevus, solar lentigo, dermatofibroma