Karyometry of melanocytic lesions: quantitative assessment of the 'maturation to the depth'.

40 cases each of malignant melanoma. Spitz's nevus and benign intradermal nevus were examined using an interactive image analysis system. 60 consecutive nuclei were evaluated in the upper and lower portion of the melanocytic lesions. Besides basic karyometric data, a 'maturation parameter' (MP) expressing the previously described 'maturation to the depth' was assessed in each individual case, by calculating the ratio of the nuclear area in the deep portion and in the superficial portion. When the three parameters (superficial nuclear area, deep nuclear area and maturation parameter) were evaluated separately (k-nearest neighbour method), the efficiency of the superficial nuclear area was only 19%, compared with 72% for the deep nuclear area and 94% for the maturation parameter. Combination of the maturation parameter and the deep nuclear area provided an efficiency of 98% with a sensitivity of 98% and a specificity of 97%. The results indicate that the maturation parameter is superior to conventional karyometric data in the differentiation between benign and malignant melanocytic lesions.