Flow cytometric DNA analysis of primary cutaneous malignant melanoma

DNA-ploidy of primary malignant melanoma was retrospectively compared by flow cytometry with sections of paraffin-embedded blocks, among tumours at different histopathological stages (levels) and among tumours and their peripheral lesion. In none of 10 melanomas at levels I-II or 10 melanocytic nevi was an aberrant DNA pattern found. In contrast, 8 of 18 melanomas at levels III-V including 6 of 9 melanomas at level V, showed a non-diploid (aneuploid) DNA pattern. However, even in these non-diploid melanomas the peripheral area showed a diploid pattern where tumour cell invasion was slight, similar to the level I-II melanomas. These results indicate that DNA-aneuploidy in melanoma is closely associated with the lesional advancement, and reflect a poor prognosis for patients with melanoma at level III or higher.