Primary malignant melanoma of the skin. Relationships of nuclear DNA content, nuclear morphometric variables, Clark level and tumor thickness.
To investigate how nuclear morphometric variables, tumor thickness (measured according to Breslow), invasion depth (classified according to Clark), nuclear DNA content and type of DNA histogram are associated with each other in primary malignant melanomas of the skin. Image analysis DNA cytometry and nuclear morphometry were performed on 85 primary skin melanomas. The relationships of size, sphericity and DNA content of melanoma cell nuclei; melanoma thickness; and Clark level were analyzed in detail. The effect of melanin bleaching on DNA cytometry results was studied. Melanoma thickness correlated with nuclear size in aneuploid, but not diploid, melanomas. The prevalence of aneuploidy did not increase with tumor thickness. In aneuploid melanomas the proportion of cells with higher-than-diploid and higher-than-tetraploid DNA content increased with tumor size. Aneuploidy is as common in thin as in thick melanomas. Genetic instability in aneuploid melanomas correlates with melanoma thickness. This correlation in aneuploid melanomas partially explains the correlation between nuclear size and melanoma thickness. In diploid melanomas no correlation was observed between nuclear size and melanoma thickness. DNA cytometry is a valuable tool for studies on the background of phenotypic changes in skin melanomas.