Nuclear size and shape parameters correlate with proliferative activity in cutaneous melanocytic tumors

Proliferative activity and morphometric data have previously been shown to be related with the degree of malignancy in melanocytic skin tumors. In the present study, the proliferative activity, as defined by Ki 67 monoclonal antibody (reactive with all actively cycling cells), has been determined by immunohistologic and morphometric methods in cutaneous melanocytic tumors. Quantitative morphologic features of Ki 67-positive and Ki 67-negative nuclei were separately assessed using computer-assisted image analysis. Comparing morphometric features and proliferative activity, the most significant correlation was found between mean nuclear volume and the percentage of Ki 67-positive nuclei in each lesion (linear regression analysis: r = 0.73; p = less than 0.05). On multidimensional discriminant analysis, tumors with high proliferative activity (more than 5 X 10(3) Ki 67-positive cells per mm3 tumor tissue) were detected at a specificity of 92% and a sensitivity of 75%. Within one lesion, Ki 67-positive nuclei showed an increase in nuclear volume (Wilcoxon test: p = less than 0.05), a more spheroid shape (p = less than 0.05), and a wider dispersion of nuclear volume values (Siegel-Tukey test: p = less than 0.05) than negative nuclei. Discriminant analysis on the basis of nuclear volume density functions facilitated an estimation of the proliferative state (resting or cycling) of a given nucleus. The results are consistent with increased cellular synthetic activity in highly proliferating lesions and particularly in actively cycling cells. The association of proliferative activity and quantitative nuclear features may be helpful in the interpretation of morphometric studies concerning melanocytic skin tumors.