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Digital computer analysis of dermatoscopical images of 260 melanocytic skin lesions; perimeter/area ratio for the differentiation between malignant melanomas and melanocytic nevi


*Corresponding author, Department of Dermatology, University Hospital, Dr E. Benese 13, 305 99 Pilsen, Czech Republic, tel. +420 377402632, +420 377402148; fax +420 377422683; E-mail:


Background  Digital computer analysis of dermatoscopical images has been reported to facilitate the differential diagnosis of pigmented skin lesions in recent years.

Objective  The aim of our study was to perform digital computer analysis of a set of different melanocytic lesions and compare the objective results.

Methods  The set of 260 melanocytic lesions (150 excised difficult cases (46 melanomas, 47 atypical nevi, 57 common nevi and 110 unexcised common nevi) was automatically analysed by the digital dermatoscopical system microDERM. We searched for differences in asymmetry, size, compactness and colour distribution. Perimeter/area ratio was calculated.

Results  The perimeter/area ratio was detected as the most important criterion for differentiation between malignant and benign melanocytic lesions (sensitivity 91.3% and specificity 90.7% for malignant melanomas vs. all benign nevi; sensitivity 91.3% and specificity 80.8% for melanomas vs. clinically atypical nevi). Differences in size of the lesion, shape and asymmetry of colour were found and statistically verified. Using step-wise logistic regression the formula for calculation of probability of malignant nature of every analysed lesion was constructed.

Conclusion  The perimeter/area ratio is a simple parameter for the differential diagnosis of melanocytic skin lesions.