Melanoma versus dysplastic naevi: microtopographic skin study with noninvasive method.

Malignant melanoma (MM) is a cutaneous tumour that originates from the epidermal melanocytes, and whose prognosis is strongly determined by tumour vertical thickness. ABCDE system is currently used for the clinical diagnosis of MM: lesion asymmetry, border irregularity, change or variegation in colour, diameter > 6mm and rapid evolution. Different methods have been used to improve the diagnosis of MM, but the results have not been convincing. Our work investigates the differences between MM and atypical naevi through skin surface analysis, using scanning electron microscopy (SEM): in fact ABCDE classical criteria are often insufficient for differential diagnosis of melanoma. In our study, we analysed 15 malignant melanomas surfaces from 15 patients and of 15 atypical naevi from 10 patients. On histological examination five superficial spreading melanoma (SSM) and 10 nodular melanoma (NMM) were found. Inclusion criteria used for selection were clinical diagnosis of SSM or clinical doubt between MM and atypical naevi (dysplastic naevi). Superficial skin texture was analysed using the silicone replica technique. The replica material is a polyvinylsiloxane derivative for dental application. Our results show that the melanoma has a very irregular surface, with a marked reduction or disappearance of cutaneous furrows, and formation of new lines with varying direction. In conclusion, the method above based on skin surface analysis, may be of help in diagnosis of early stage MM and in differentiating from atypical naevi.