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.