Mosaic subclinical melanoderma: an Achilles heel for UV-related epidermal carcinogenesis?

Cutaneous cancers are not uncommon on the face of elderly patients. Melanin should protect, at least in part, against the ultraviolet (UV)-induced neoplastic damage. However, the density in melanin chromatophores is heterogeneous in the epidermis of Caucasian adults. The computerized UV light-enhanced visualization (ULEV) method is a sensitive tool to assess non-invasively this mosaic pattern of intra-epidermal melanin load. In this study, the combination of ULEV pattern analysis and image analysis were performed involving four groups of phototype III Caucasian subjects. The first group was composed of 55 patients aged from 65 to 75 years who suffered from several malignancies of facial skin. The second control group of 55 patients who never had developed skin cancers were matched with the first group for age, sex and phototype. The third group was composed of 80 patients aged from 49 to 59 years who had developed a single basal cell carcinoma. The fourth group comprised 80 age, sex and phototype-matched healthy control subjects. Irrespective of the groups of subjects, a correlation was found between the pattern grading and the objectively determined relative area of subclinical melanoderma. Patients with multiple skin cancers differed from the other groups by the fact that a significantly higher proportion of them exhibited an extensive type of subclinical melanoderma. This feature was also seen in a minority of patients with a single basal cell carcinoma. The extensive subclinical melanoderma pattern is interpreted as a clue for risk, but not as a cause of UV-induced skin carcinogenesis.