P90 exceeding rate as a prognostic factor in primary malignant melanoma of the skin. A DNA image cytometric study.

OBJECTIVE: To study the prognostic value of DNA image cytometry in primary skin melanomas. STUDY DESIGN: DNA image cytometry was performed on 62 stage I, Clark level II-V, primary skin melanomas. The DNA histograms were classified into three categories (diploid, nondiploid and aneuploid) according to the percentages of cells with higher-than-diploid and higher-than-twice-the-diploid DNA content (the P90 and 2P90 exceeding rates [ERs]). The prognostic value of P90ER, 2P90ER, type of DNA histogram, melanoma thickness, Clark level, and patient age and sex were analyzed for disease-specific survival with Cox's stepwise proportional hazards model. RESULTS: Aneuploid DNA histograms were as common in thin as in thick melanomas. Melanoma thickness and P90ER had prognostic value in univariate analysis, but in the multivariate analysis only P90ER had independent and significant prognostic value. CONCLUSION: Aneuploidy is a common feature of malignant melanoma, and it is as common in thin as in thick melanomas. P90ER has more prognostic value than the type of DNA histogram. The prognostic value of P90ER as compared with melanoma thickness should be studied further.

Primary malignant melanoma of the skin. Relationships of nuclear DNA content, nuclear morphometric variables, Clark level and tumor thickness.

OBJECTIVE: 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. STUDY DESIGN: 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. RESULTS: 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. CONCLUSION: 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.

Nuclear morphometry, immunohistochemical staining with Ki-67 antibody and mitotic index in the assessment of proliferative activity and prognosis of primary malignant melanomas of the skin.

Nuclear morphometry, immunohistochemical staining with Ki-67 antibody and mitotic index were studied in primary cutaneous malignant melanomas. The number of Ki-67 positive cells/ 200 tumor cells did not correlate with any nuclear morphometrical parameters, and it only approached but did not reach significant correlation with melanoma thickness according to Breslow. The nuclear area, short axis and long axis correlated with melanoma thickness, but the nuclear axis ratio (which reflects the sphericity of nuclei) and melanoma thickness did not show significant correlation. Mitotic index was higher in thick melanomas and in melanomas with high Ki-67 positivity, large nuclear area, long nuclear short axis, and small nuclear axis ratio. In Cox's stepwise proportional hazard model, melanoma thickness and the nuclear axis ratio were significant independent prognostic factors for patient survival, while the nuclear area, short axis and long axis, gender, age, Clark level, mitotic index and Ki-67 positivity lacked significant independent prognostic value. The results suggest that the proliferative activity of tumor cells does not alone explain the great importance of tumor thickness as prognosticator in melanoma. The thickness of melanoma measured according to Breslow and the nuclear axis ratio are more efficient prognosticators in melanoma than parameters associated with proliferation.

Bleaching of melanin before image cytometry of the DNA content of pigmented skin tumors.

OBJECTIVE: To study the effect of bleaching of melanin with KMnO4 on the results of DNA image cytometry in pigmented skin tumors. STUDY DESIGN: Image cytometry of nuclear DNA content was performed on sections from 14 melanocytic skin tumors stained with Feulgen stain both with and without prior bleaching with KMnO4. RESULTS: The nuclear staining intensity of Feulgen stain was lower in the bleached sections, but this did not significantly affect the evaluation of ploidy. Heavy pigmentation caused some false peaks in the histograms (4 of 28 measurements made on unbleached slides). CONCLUSION: Bleaching of sections with KMnO4 can be useful when heavy melanin pigmentation would make DNA measurements impossible or difficult in image analysis cytometry. Bleaching is not advisable when only lightly pigmented tumors are analyzed if nuclei obscured by any pigment granules are to be avoided. In large series containing both bleached and nonbleached specimens, statistical analysis of these groups should be separated.