Evaluation of DNA ploidy and degree of DNA abnormality in benign and malignant melanocytic lesions of the skin using video imaging

Abstract

Making a morphologic distinction between benign and malignant melanocytic tumors of the skin is frequently difficult, especially because "gray zones" between these lesions often exist. DNA image cytometry as an adjuvant method for the diagnosis and prognostic prediction of premalignant lesions and malignant tumors of many other organs is already well established. The aim of this study was to determine whether DNA image cytometry is helpful in distinguishing benign from malignant melanocytic lesions and whether cytometry would give valid information with which to predict the prognoses associated with malignant melanomas. DNA image cytometry was performed on 127 benign and 58 primary maligant melanomas of the skin as well as 11 metastatic melanomas, using an enzymatic single cell solution according to a method described by Heiden et al. in Cytometry (1991;12:614-21). DNA aneuploidy was graded by DNA index (DI) and a 2c deviation index (2cDI). In contrast to benign melanocytic lesions (with 16% DNA aneuploidy), primary and metastatic malignant melanomas had significantly higher frequencies of DNA aneuploidy (86% and 73%, respectively). In the degree of DNA aneuploidy, significant differences between benign and malignant melanocytic tumors could be observed. The mean 2cDI of aneuploid benign lesions was 1.0, whereas the primary malignant melanomas had a mean 2cDI of 2.92 and the metastatic melanomas a mean of 6.9. The frequency of DNA aneuploidy increased with Breslow thickness. Twenty-one patients with primary malignant melanoma developed metastases. All metastasizing primary tumors were aneuploid and showed a significantly higher grade of DNA aneuploidy than nonmetastasizing malignant melanomas. Moreover, none of the diploid malignant melanomas developed metastases. This study reveals that DNA image cytometry is prognostically and diagnostically relevant to the evaluation of melanocytic lesions of the skin. Nevertheless, it cannot be relied on alone to provide enough information for a diagnosis.