Surface microscopy of naevi and melanomas—clues to melanoma

Summary In this present study. 260 histologically conlirmed melanocytic skin tumours (188 benign nacvi and 72 malignant melanomas; from 1989 to 1990) were investigated with regard to valid surface microscopical criteria of malignancy. The tumours were analysed using a system which assessed eight components. Most melanomas were characterized by the following pattern: asymmetrical pigment distribution, more than three colours, black pigment, peripheral stripes, and asymmetrical depigmentation. The results were evaluated statistically by contingency tables and logistic regression procedures. On the basis of the classification derived, the sensitivity and specificity were determined for lesions from 1991. and were 0·9 and 0·85, respectively. Many melanocytic naevi were not identified by the above criteria, or were found only occasionally. Pigment network was often absent in naevi and melanomas, and was not decisive for the diagnosis. The present investigation demonstrates that in vivo diagnosis of pigmented melanocytic lesions can be improved by surface microscopy.