PROLIFERATION MARKER KI-S5 AS A DIAGNOSTIC-TOOL IN MELANOCYTIC LESIONS

Background: A discrimination between benign and malignant melanocytic lesions is not always possible by conventional histology. Objective: O ur purpose was to determine the proliferative activity in various type s of melanocytic neoplasms and to appraise its value as a diagnostic a djunct. Methods: The growth fraction was assessed immunohistochemicall y in 398 melanocytic lesions by means of the monoclonal antibody Ki-SS directed to the Ki-67 antigen. In this way, a cut-off level was defin ed and applied to 112 lesions of equivocal histology. The revised diag noses were correlated to the clinical courses. Results: Common nevi, S pitz nevi, and melanomas exhibited significantly different proliferati on indices and distinctive distribution patterns of cycling cells. In agreement, malignancy diagnosed on the basis of a growth fraction grea ter than 5% was confirmed by disease progression in 68% of our cases w ith uncertain diagnosis. Conclusion: Determination of the proliferativ e activity in melanocytic lesions may usefully complement conventional histology to improve diagnostic accuracy.