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

BACKGROUND. Making a morphologic distinction between benign and malignant m elanocytic tumors of the skin is frequently difficult, especially because " gray zones" between these lesions often exist. DNA image cytometry as an ad juvant method for the diagnosis and prognostic prediction of premalignant l esions and malignant tumors of many other organs is already well establishe d. The aim of this study was to determine whether DNA image cytometry is he lpful in distinguishing benign from malignant melanocytic lesions and wheth er cytometry would give valid information with which to predict the prognos es associated with malignant melanomas. METHODS. DNA image cytometry was performed on 127 benign and 58 primary mal ignant melanomas of the skin as well as 11 metastatic melanomas, using an e nzymatic single cell solution according to a method described by Heiden et al. in Cytometry (1991;12:614-21). RESULTS. DNA aneuploidy was graded by DNA index (DI) and a 2c deviation ind ex (2cDI). In contrast to benign melanocytic lesions (with 16% DNA aneuploi dy), primary and metastatic malignant melanomas had significantly higher fr equencies of DNA aneuploidy (86% and 73%, respectively). In the degree of D NA aneuploidy, significant differences between benign and malignant melanoc ytic tumors could be observed. The mean 2cDI of aneuploid benign lesions wa s 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 inc reased with Breslow thickness. Twenty-one patients with primary malignant m elanoma developed metastases. All metastasizing primary tumors were aneuplo id and showed a significantly higher grade of DNA aneuploidy than nonmetast asizing malignant melanomas. Moreover, none of the diploid malignant melano mas developed metastases. CONCLUSIONS, 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 informa tion for a diagnosis. Cancer 2000;88:1370-7. (C) 2000 American Cancer Socie ty.