Why are scars pale? An immunohistochemical study indicating preservation of melanocyte number and function in surgical scars.

The cosmetic effect of many mature scars is largely due to their paler appearance than the surrounding skin. The aim of the study was to identify whether melanocytes are present and functioning within pale scars. Cryosections from scar and normal tissue were stained with murine monoclonal antibodies mel-5, c-kit and NKI/beteb to detect melanocytes and precursor melanocytes. The mean number of mel-5 immunopositive melanocytes within scar tissue was similar to that seen in normal skin (26, SEM 3.5, versus 28.9, SEM 4.1, per 200 basal cells). Where paired samples were available, there was no statistically significant difference between scar tissue and adjacent skin (95% CI = -7.8 to +4.6, p=0.53). Masson-Fontana stain for melanin was positive in both scar tissue and adjacent normal skin, with no evidence for differences in melanin transfer to keratinocytes. Our results suggest that neither differences in melanocyte number nor melanogenic activity explain the appearance of scars. It would seem likely that a combination of both vascular and optical factors relating to dermal or epidermal characteristics are more important.