SUCCESSFUL DIFFERENTIATION OF SPITZ NEVUS FROM MALIGNANT-MELANOMA BY MICROFLUOROMETRIC ANALYSIS OF CELLULAR DNA CONTENT

Two cases of presumed Spitz naevus, whose diagnosis on clinical and hi stological grounds was uncertain, were examined for cellular DNA conte nt using the technique of DAPI-DNA microfluorometry. They were compare d with 20 cases, respectively, of clinically and histologically confir med, Spitz naevus, malignant melanoma and acquired pigmented naevus. T he two Spitz naevi showed a diploid pattern in a distribution histogra m of cellular DNA content. The pattern was similar to that of confirme d Spitz naevi and of acquired pigmented naevi but different from the a neuploid pattern of malignant melanomas. DNA index values of the two c ases were within the range of confirmed Spitz naevi and different from those of malignant melanomas. The DAPI-DNA microfluorometric method t hus provided confirmatory evidence for the diagnosis of Spitz naevus. The method appears to reflect sensitively the biological behaviour of tumour cells, and is a useful aid to the diagnosis of uncertain Spitz naevi.