TNF and halo nevus: This difference with respect to regressing melanoma was attributed to the different cytokine microenvironment; in fact, fibrogenic cytokines such as IL-6, TGF-β, TNF-α, bFGF and PDGF are expressed by melanoma while TNF-α, an antifibrogenic cytokine, was found to be more expressed in the halo nevus [29].