DNA-ploidy abnormalities are a reflection of the metastatic potential of malignant melanoma. Microfluorometric DNA analysis.

Abstract

Using DAPI (4',6-diamidino-2-phenylindole)-DNA microfluorometry, we examined the nuclear DNA-ploidy abnormalities of 15 primary malignant melanomas and their 20 corresponding metastases. They all presented the aneuploid DNA histographic pattern. When the DNA index value was calculated as the reflection of DNA-ploidy abnormalities, it was found to be significantly higher in the metastases (2.07 +/- 0.50) than in the primary tumors (1.76 +/- 0.50) (p < 0.01). Sixteen (80%) of the metastatic tumors had a higher DNA index value than their primary tumors, whereas the remaining four (20%) had a lower value. The difference in the DNA index values between the primary and metastatic tumors did not correlate to any other conventional prognostic variables (e.g. histologic type, level, and thickness). When we added 15 non-metastatic melanomas to the above 15 primary melanomas and evaluated the predictors for metastasis using multivariate stepwise logistic regression analysis, the DNA index value of the primary melanomas was found to be the most reliable risk factor. These results suggest that primary melanoma cell populations, having high DNA index values, are usually responsible for subsequent metastasis, and that hence, DNA-ploidy abnormalities of primary melanomas are likely to provide useful information for patient potential with regard to metastasis.