The fascinating biologic phenomenon of regression in melanoma is dermoscopically reflected by white areas, blue areas and a combination of both. White areas, formerly called white scar-like areas, are more or less well-circumscribed white zones resembling a superficial scar. Blue areas, synonymously named gray-blue areas, peppering, or multiple blue-gray dots, are small diffuse or speckled zones with a gray-blue or gray coloration. A particular pitfall when assessing the so-called combinations of white and blue areas is the fact that this combination is virtually indistinguishable from the blue-whitish veil.

Histopathologic correlates

Histopathologically, regression of melanoma is characterized by fibrosis and/or variable amounts of melanophages within a thickened papillary dermis. So, white areas correspond to fibrosis and blue areas to melanosis. However, since fibrosis and melanosis are commonly found together, combinations of white and blue areas are often noted also dermoscopically.

Diagnostic significance

White areas, blue areas and especially the combination of both features are rather specific dermoscopic criteria for melanoma. However, regression structures may be occasionally found in Clark nevi and, in such instance, the differentiation from regressive melanoma may be difficult not only dermoscopically but also histopathologically. Regression structures, especially of the melanosis type, may be found in lichen planus-like keratosis or in pigmented actinic keratosis and may basically be indistinguishable from melanoma with regression.