Basal cell carcinomas were observed in six patients within the area of erythrosis interfollicularis colli, but only one tumor was localized in the area of cutis rhomboidalis nuchae.
Erythrosis interfollicularis colli and cutis rhomboidalis nuchae are two skin diseases associated with chronic exposure to sunlight and are more frequent with increasing age.
Erythrosis interfollicularis colli has a peculiar dermoscopic finding: the perifollicular white halo, or a well-defined, round, homogeneous whitish area surrounding the follicular opening of the hair follicle (the "full-moon sign"; Fig.
This could explain why no erythrosis interfollicularis colli was observed in patients with Fitzpatrick skin type I.
The distribution of basal cell carcinomas and actinic keratoses of the neck and upper trunk argued for a local skin cancer protective effect of cutis rhomboidalis nuchae but not of erythrosis interfollicularis colli (7, 8).