Epithelioid cell melanomas have greater DNA ploidy abnormalities than spindle cell melanomas: cytological evidence for a higher malignant potential of the former.

The cellular DNA ploidy of 30 cases of malignant melanoma was measured by 4',6-diamidino-2-phenylindole-DNA (DAPI-DNA) microfluorometry. DNA histograms and DNA index values were compared among melanomas of different cell morphology. Epithelioid cell melanomas often showed greater DNA aneuploidy than spindle cell melanomas in terms of histographic pattern. DNA index values of the former (mean +/- standard error, 1.84 +/- 0.31) were significantly higher than those of the latter (1.55 +/- 0.24; P < 0.05). The DNA index values of mixed-type melanomas were intermediate. These results indicate that the epithelioid cell melanomas have greater DNA ploidy abnormalities which are usually correlated with a greater malignant potential in pigmentary neoplasms. Thus our results confirm clinical evidence that melanoma patients with the epithelioid type of cells have a poorer prognosis than those with the spindle type of cells.