[Problems in defining melanoma regression and prognostic implication].

Between 10 % and 35 % of all melanomas show histological regression. That is, there is an area within the melanoma where the tumor retreats or disappears to be progressively replaced by fibrosis with presence of melanophages and variable degrees of inflammation, and neovascularization. Such regression is generally considered an indicator of poor prognosis in melanoma, although a number of studies contradict this affirmation. In this review, we summarize the leading articles about the influence of regression on melanoma prognosis. The results of these studies are very inconsistent, and so the prognostic significance of regression is somewhat controversial. We believe that some of these differences can be explained by differing criteria for regression and so we propose clear histological criteria to define early and sustained regression.